Pink Bubble Strawberry Butter Cake

Pink Bubble Strawberry Butter Cake...a delightfully pink ombré cake topped with pink bubbles. Buttery, filled with strawberry compote and whipped vanilla cream, this cake evokes birthday parties and celebrations...

This cake was pretty exciting to make. It was a cake of firsts. The first cake I photographed with my brand new camera. The first time I made gelatine bubbles. My first ombré cake. And I think that's all the firsts but 3 firsts is still very impressive for one cake. I started dreaming of a very pink cake a few weeks ago when my sister had her baby girl. I thought a pink cake was in order to celebrate. But then, why should I start pushing gender conformity on a 5 week old baby? We'll just have to set that aside and embrace the pinkness for now...cos it's SO PRETTY! Look at the pinkness! YAY!

I've called this the Pink Bubble Strawberry Butter Cake. My go-to vanilla cake is usually an adaption of the amazing Sweetapolita's vanilla cake but this time, I wanted a buttery, dense cake which would stay firm and soak up the strawberry compote I was planning on filling the cake with. So I used a very traditional butter cake recipe, which would have enough firmness to soak up liquid while being stacked high. It's a lovely simple cake that suits many different icings and uses.

Now to the really fun and messy bit! These gelatine bubbles were so much fun to make and really easy. They need 24 hours to dry so make sure you start them a day or two before. You could even do them a week in advance and store them in a dry, air tight container. As long as you don't get them wet, they could really survive indefinitely. And just a note that although they are technically edible, they would be really gross to eat.

To make the bubbles, blow up some water balloons of varying sizes. I found that to make them really round, blow to the desired size then twist the "stem" of the balloon really tight, pushing the air to the other end and tie them tight. Pierce the excess plastic with a skewer and push the other end into a sponge, so that the balloons are suspended above your bench, not coming into contact with each other. 

Then mix up your gelatine mixture. I'll put really detailed instructions below but basically, the ratio is two parts water to one part powdered gelatine. For this many bubbles, I used 6 tablespoons of water and 3 tablespoons of gelatine. After you've coloured the gelatine, let it set and then microwaved the geltain, dip your balloons in the mixture. For my bubbles, I dipped some once and some twice. The more you dip them, the darker they'll be.

Don't worry if the under side of your bubbles are a bit mess, they'll be sitting on the cake and I found i had to trim those bits off to get them to sit flat anyway. Just try to make the upper-side as smooth as possible. Even then, one of my favourite bubble had a ripple through it from not being dipped smoothly enough. Imperfections can be the best...there's a lesson for my niece to learn! 

The next day, pop the balloons and peel them away from the bubble. This bit was really fun. 

Then it's on to the cake, filling and icing! 

And because this is a celebration cake, it deserves a special icing. I decided to make a vanilla Swiss meringue buttercream. Many people prefer this SMBC over regular buttercream, however real buttercream with tonnes of icing sugar and butter will never be usurped in my heart. But SMBC is a lovely icing and a real skill to add to your baking repertoire. It's more stable and can withstand a hotter day then traditional buttercream. Lots of people use it for wedding cakes in Australia where our days can get so warm. It's also got a lighter texture and can be a little easier to get smoother finish on your cake. 

The cake is filled with fresh strawberry compote and a good dollop of whipped cream. I wanted the cake to evoke strawberry shortcake. Even though I've never had proper strawberry shortcakes...I think I'll need to have a go at that soon. The whipped cream has a little gelatine in it to stabilise it, it need to hold it's own under 5 layers of dense cake!
The cake is really easy. I did find it domed quite a bit, even with bake even strips so you might need to do a little trimming to get the cake layers nice and flat. But then you get to eat the trimmings so really not that bad of a deal. 

The icing is a little different to traditional buttercream. You start by placing the egg whites and sugar in a heatproof bowl. As the whites and sugar get whipped after they're heated, I just use my metal KitchenAid bowl. Heat the egg whites and sugar over a rapidly simmers pot of water, gently whisking constantly, til they reach 60°C/140°F on candy thermometer or until there are no grains of sugar left. You need to make sure you are whisking constantly, otherwise you'll end up with really sweet scrambled eggs.

After this, whip the egg whites with a whisk attachment of a stand mixer, or with handheld beaters. They need to whisked until they return to room temperature, around 8-10 minute. Once the whites and bowl are neutral to the touch, add bits of cool - not soft - butter in 30 second intervals until all mixed. Then the Swiss meringue buttercream is ready! This whole process can be a little intimidating but once you have it, it's really easy. Like a lot of things in life! Another lesson for baby! But if you're having troubles, the ever amazing Sweetapolita has the best and clearest step by step to follow. I strongly encourage you to go have a read of them if it's your first time making SMBC.

After you've made the icing and trimmed your layers, stack them on top of each other, filling each layer with cream and strawberry compote...

Now we've assembled the cake, it's time to start the ombré icing. I started by tinting the whole lot of the icing a base pink shade. I then used this to do a crumb coat over the whole cake, making sure the cream dam was reinforced by SMBC. Put the cake in the fridge to firm up for 30 minutes. 

In the meantime, split your remaining SMBC into 3 lots and tint them to the desired shades. Remember, add a little icing at a time. It's easy to add more, not so easy to take away. 

Once the cake is firm and you're happy with your icing shades, it's time to ombré! Add the darkest icing on the bottom third of the cake...

...the medium colour on the middle of the cake...

...and the lightest colour on the top third and top of the cake. 

This is where having a turntable comes in handy. Mine is cheap and has warped but it shouldn't matter too much as long as it spins. Spin the cake around and around, holding a bench scraper perpendicular to the cake. As you spin and smooth the cake, the layers will blend and become ombré. So pretty! 

Top with the bubbles. I used a mix of pink and silver cachous to fill in the gaps.

And there you have it! A wonderful Pink Bubble Strawberry Butter Cake!

Perfect for a birthday party or just because! 

How sweet do the water balloons look blown up...

I'm already thinking of the cake I'll make for baby's first birthday.

I'm loving the new camera by the way. I think there's a lot to learn with food photography and I'm so excited to jump in!

Yummy, sweet, buttery...

And one more cos I just LOVE my new camera!

Pink Bubble Strawberry Butter Cake

*Make gelatine bubbles at least 24 hours before required to ensure adequate drying time
*To ensure even layers, weigh your mixing bowl before beginning cake mix. This will make it possible for you to subtract the weight of the bowl from the total weight once the cake batter has been made and allow you to divide the batter into fifths. 

Prep time: 140 mins plus drying time

Cooking time: 90 mins

Total time:  3 hr 50 mins 

Servings: 12

Gelatine Bubbles
Water ballons
Wooden skewers
Large sponge
Vegetable oil
3 tablespoons powdered gelatine
6 tablespoons cold water
Pink gel food colouring

1. Fill 10 - 20 water balloons with air, inflating to various sizes. Pinch and twist opening of balloon to push the air down to the end of the balloon to ensure a round shape.
2. Pierce the excess end of the balloon with a wooden skewer and push into a sponge to ensure that the balloons are not touching to ground or each other.
3. One by one, rub the outside of the balloons with a tiny amount of vegetable oil. Wipe the excess off the balloons with a paper towel.
4. In a small microwave proof bowl, mix together the gelatine, water and food colouring. Allow to absorb for 5 minutes.
5. Heat the gelatine mix in the microwave in 10 second intervals until the geltaine is melted and the mix is smooth.
6. Allow to cool slightly then holding the balloon by the know, dip each balloon in the gelatine until the balloon is mostly covered.
7. After all balloons have been dipped, dip about half of the balloons again to darken the colour.
8. Allow balloons to dry overnight.
9. Once the balloons are dry, pierce the balloon and deflate the balloon inside the gelatine. Peel away the balloon and trim the gelatine bubbles to sit flat.
10. Store in an airtight container til required.

Butter Cake
375g butter, softened
3 cups caster sugar
6 eggs, free range
1 1/2 teaspooons vanilla extract
4 1/2 cups plain flour
1 teaspoons baking powder
1 teaspoon bicarbonate soda
1/2 teaspoon salt
1 1/2 cups buttermilk

Swiss Meringue Buttercream
7 large/225g egg whites, free range 
1 1/2 cups/375g caster sugar
2 1/2 cups/510g butter, cut into 2cm cubes - should be cool, not cold. Take butter out of fridge 10 -15 minutes before required.
2 teaspoons vanilla
Pink gel food colouring

Strawberry Compote
2 cups chopped strawberries
1/2 cup sugar
1 tablespoon lemon juice

Whipped Cream Filling
2 tablespoons cold water
2 tablespoons powdered gelatine
420ml thickened cream
1/4 cup sifted icing sugar
1 teaspoon vanilla

Butter Cake

1. Preheat oven to 180°C.
2. Grease two 8 inch/20cm cake tins generously with butter and flour the sides. Line the bases with baking paper
3. In the bowl of an electric mixer, beat the butter and caster sugar until creamy and lighter in colour.
4. Add the eggs, one at a time, until each egg is mixed through
5. Add vanilla and beat until just combined.
6. In a separate bowl, sift together flour, baking powder, bicarbonate soda and salt.
7. Add the sifted flour and buttermilk to the butter mix alternately, starting and ending with the flour. Beat on a low speed until just combined.
8. Using scales, divide the batter into 5 lots and bake the first two cakes for 45 - 50 minutes, or until the tops are golden and a wooden skwer comes out clean when cake is pierced.
9. Allow cakes to stand in the pans for 10 minutes before turning on to racks to cool.
10. Clean the cake pans, re-grease and line, then bake next two layers, then the final layer.
11. Allow cakes to completely cool before trimming as required.

Swiss Meringue Butter Cream

1. Wipe out the metal bowl of stand mixer with a paper towel moistened with lemon jucie to ensure the bowl is grease free.
2. Add egg whites and sugar, and simmer over a pot of rapidly simmering water, whisking gently until temperature reaches 60°C or until sugar is dissolved.
3. Take the bowl off the heat and put onto stand mixer. Whip on a medium speed until the egg whites have cooled to room temperature. This will take 8 - 10 minutes, or more. Do not add butter until bowl is neutral to the touch.
4. Switch over to paddle attachment and with mixer on low speed add butter cubes one by one in 30 second intervals until all butter has been added. 
5. If the mixture becomes lumpy and looks like scrambled eggs, do not panic. Keep mixing on a low speed and the mix will come together and become smooth. 
6. Add vanilla and a small amount of pink food colouring to reach desired base shade.
7. Set aside until required.

Strawberry Compote

1. Add chopped strawberries to a medium pan along with sugar and lemon juice.
2. Simmer gently, til strawberries break down and mix becomes jam like, around 5 - 8 minutes.
3. Set aside to cool, then refrigerate until required.

 Whipped Cream Filling

1. Add gelatine to a small bowl and then add cold water. Mix and set aside for 10 minutes.
2. In a small saucepan, heat 1/2 cup cream until it just begins to simmer then take off the heat and add gelatine. Whisk to combine and then place in fridge.
3. Keep whisking the gelatine and cream every 2 minutes, placing back into the fridge in between, until the cream reaches a cool temperature.
4. Whip the remaining cream with icing sugar until soft peaks just begin to form.
5. Very gradually add the cool gelatine and cream mixture while beating and continue beating until medium-firm peaks form. Once medium peaks being to form, cease beating or cream with turn lumpy. Refrigerate until required.

Assembly

1. Place one layer of cake onto a cake board, cut side up.
2. Pipe a layer of the whipped cream filling around the border of the cake to create a "dam" for the strawberry compote,
3. Spoon 1/4 of the strawberry compote into the cut side of the cake. Add a few random dollops of cream on top of the compote,
4. Add another layer of cake and repeat with cream and compote. Repeat until all layers are added.
5. With the Swiss Meringue Buttercream, fill in any gaps between the layers and ensure sides of the cake are straight.
6. Using a spatula, add a thin layer of Swiss Meringue Buttercream to the outside of the cake, creating a crumb coat over the entire cake.
7. Refrigerate cake for 30 minutes.
8. Divide the remaining Swiss Meringue Buttercream into thirds and tint each third desired shade.
9. Take cake out of the fridge and add the darkest coloured icing to the bottom third of the cake, the medium shade to the middle third and the lightest colour to the top third and top of the cake.
10. Holding a straight cake scraper, bench scraper or spatula 90 degrees to the cake.
11. Slowly spin the cake til colours have blended and outside of the cake has reached the desired smoothness. You may need to refrigerate the cake to firm up, to allow pressure to be applied to smooth the cake.
12. Top with gelatine bubbles and coloured sprinkles.