Sprinkle sponge cake with whipped vanilla buttercream

Whenever I crave cake, this is exactly the sort of cake I am after. Birthday cake with coloured sprinkles; what more could you want? Heavy on the vanilla and topped with a light, whipped buttercream, it may look plain and simple but there is nothing plain and simple about the taste! Sometimes less really IS more, particularly when it allows an ingredient like vanilla, which is so often bolstered by layers of more dominant flavours.

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I’ve used the reverse creaming method for the sponge of this cake, as it produces a really tender, soft sponge with a tight crumb that melts in the mouth. Another bonus is that it will keep moist much longer than a traditional sponge, which is ideal for sheet cakes as they tend to be thinner than traditional layer cake sponges. Before you freak out about creaming in reverse, relax! It’s just as simple as a normal sponge, and I personally love it as it is made from cubed cold butter so you don’t even need to bring it to room temperature. If you’ve got a stand mixer, be sure to utlise it for making this style of cake, as the paddle attachment will do all the ‘rubbing in’ work for you. If you don’t, fret not, simply rub the cubes of butter into the dry ingredients as if you are making pastry.

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The frosting, oh, the frosting. Or icing, as we like to refer to it in the UK. It is HEAVENLY! I often find buttercream too intense when piled high on a cupcaked or smothering a layer cake until it can hardly breathe, but the ratio on a sheet cake works perfectly, as your teeth sink through that crispy top (is it just me that loves it when buttercream hardens slightly on top? into a cloud of the lightest buttercream and finally into velvety smooth cake crumbs. The secret ingredient to getting that cake-batter, fresh from the bakery flavour is, wait for it - almond extract! Even if almonds are far from your favourite thing, this really changes the game as the distinct, sweetly buttery flavour of the extract combined with vanilla brings something very special to the frosting party!

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Finally, a word on ingredients. I’m a bit of a non-traditional baker in the sense that I make most of my cakes with salted butter as I love the sweet’n’salty combination it brings. One of the only places I wouldn’t use it is in buttercream, as butter is such a major component and too much salt can overpower the cake. For ease, i’d recommend using unsalted butter for both the sponge and buttercream (so you don’t get them muddled!), but be sure to add the table salt suggested in the recipe or you’ll end up with a sickly sweet cake.

I make the cake in a 23 x 23cm/9 x 9 inch square cake tin, but if you’d like to scale up to a 33 x 23cm/ 13 x 9 inch rectangular pan, you need to scale up the recipe by 1/3rd (see below for conversions!).

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Sprinkle sponge cake with whipped vanilla buttercream

Makes 9 large squares (out of 9x9inch/23x23cm square cake)


Ingredients:

For the sponge:

80g unsalted butter, cold and cut into cubes

200g caster sugar

200g plain flour

2 tsp baking powder

1/2 tsp salt

200ml milk

2 large eggs

1 tsp vanilla extract/vanilla bean paste (I use this one by Nielsen Massey: https://amzn.to/2Mt4Qoi)

For the buttercream:

100g unsalted butter, at room temperature

350g icing/confectioners sugar, sifted

2 tablespoons whole milk or double cream

1 teaspoon vanilla bean paste

1/2 teaspoon almond extract

1/4 teaspoon table salt

Multicoloured confetti sprinkes (I use these from Scrumptious Sprinkles!)

Method:

1.   Preheat the oven to 180C/160C fan. Grease and line a 23 x 23cm cake tin with baking parchment.

2.   Place the cubes of cold butter, sugar, flour, baking powder and salt into the bowl of a stand mixer with paddle attachment. Mix on low until all the butter is rubbed into the dry mixture and it has a sandy texture. You could do this step by hand, rubbing the butter into the dry ingredients as if you were making pastry.

3.     In a small jug, beat together the milk, eggs and vanilla. Pour the mixture down the side of the dry ingredients and beat until everything is mixed together. When all the liquid has been added, beat on a high speed for 2 minutes until it is really well combined and smooth. If doing this by hand, use an electric hand whisk hand whisk until smooth and creamy.

4.     Pour the mixture into the prepared tin and bake in the preheated oven for 20-25 minutes until golden brown and a skewer inserted comes out clean. Allow to cool completely whilst you make the buttercream.

5. To make the buttercream, place the butter into a large bowl or the bowl of a stand mixer and whisk on high until soft (this makes it easier to incorporate the sugar). Add half the sugar and beat slowly until combine, then add half the milk/cream and beat again. Repeat until the milk and sugar is used up, then add the vanilla, almond extract and salt and beat on high for at least 5 minutes, until really light and fluffy. Be sure to scrape the bowl down often to catch any stubborn, unmixed patches.

6. Use a palette knife to spread the buttercream over the cooled cake, then top with sprinkles. This cake will keep in an airtight container for up to 1 week!

Quantities for a 13 x 9 inch tin:

120g unsalted butter, cold and cut into cubes

300g caster sugar

300g plain flour

3 tsp baking powder

3/4 tsp salt

300ml milk

3 large eggs

1 1/2 tsp vanilla extract/vanilla bean paste

Don’t forget to tag @marthacollison and #BakingMartha if you give it a go!