Katarina says: “The initial version of this cake relied on only cocoa powder for the chocolate flavour. I won’t lie – it felt like cheating. As delicious the cake was, cocoa powder simply doesn’t match actual melted chocolate when it comes to giving a cake that deep, luxurious chocolate flavour.

“In this improved version, I’ve used both melted chocolate and cocoa powder in the sponges as well as in the frosting – and all of a sudden, it’s become every chocoholic’s dream come true. Because chocolate has a slightly acidic pH, it helps boost the activity of the raising agents and helps makes the sponges even more tender and delicate, without venturing into crumbly, falling-apart territory.

“Don’t be scared by the addition of hot water to the cake batter – together with the milk, it helps keep the cake incredibly moist, so that it simply melts in your mouth.”

Serves 12–14

Prep time: 1 hour

Bake time: 35 mins

Ingredients

For the chocolate sponges:

280g dark chocolate (60–70% cocoa solids), chopped
200g unsalted butter
250g caster sugar
4 eggs, at room temperature
160g gluten-free flour blend
80g almond flour
40g Dutch processed cocoa powder
2 tsp baking powder
1 tsp bicarbonate of soda
½ tsp xanthan gum
½ tsp salt
120g hot water
120g whole milk, warmed

For the chocolate buttercream:

600g unsalted butter, softened
400g icing sugar
100g Dutch processed cocoa powder
½ tsp salt
300g dark chocolate (60–70% cocoa solids), melted and cooled

Method

For the chocolate sponges, adjust the oven shelf to the middle position, preheat the oven to 180°C and line two 20cm round cake tins with baking paper.

In a heatproof bowl above a pan of simmering water, melt the dark chocolate and butter together. Set aside to cool until warm, then add the sugar and eggs, and mix well.

Sift in the gluten-free flour blend, almond flour, cocoa powder, baking powder, bicarbonate of soda, xanthan gum and salt. Mix well until you get a smooth batter with no flour clumps.

Add the hot water and milk. Whisk well until combined.

Divide the batter equally between the prepared cake tins and bake for about 35–40 minutes or until an inserted toothpick comes out clean.

Allow to cool in the cake tins for 10 minutes, then turn out on to a wire rack to cool completely.

For the chocolate buttercream, in a stand mixer with the paddle attachment or using a hand mixer fitted with the double beaters, beat the butter for 2–3 minutes. Sift in the icing sugar and beat for a further 5 minutes until pale and fluffy.

Sift in the cocoa powder and salt, and beat until evenly distributed.

Finally, add the melted and cooled chocolate and beat until you get a rich, smooth chocolate buttercream.

Assembling the cake

If the sponges are domed, level them using a sharp, serrated knife.

Place the bottom sponge layer on a cake stand and spread a generous layer of buttercream on top, but leave enough buttercream for the outside of the cake. Sandwich using the other sponge layer, turned so that its bottom faces upwards. This will give the cake a nice, flat surface for decoration.

Use the remaining chocolate buttercream to cover the outside of the cake. Decorate the cake by creating swirls of buttercream with an offset spatula or the back of a spoon.

Storage

3–4 days in an airtight container or wrapped in cling film in a cool, dry place or the fridge. If you keep the cake in the fridge, leave it out at room temperature for about 15 minutes before serving.

Put a twist on it

Milk chocolate cake – in the sponges, replace the dark chocolate with milk chocolate (for best results, melt the milk chocolate and butter separately), reduce the sugar to 200g, increase the gluten-free flour blend to 240g, and omit the cocoa powder. In the buttercream, replace the dark chocolate with milk chocolate and reduce the cocoa powder to 40g (but add it slowly until you get the desired flavour and colour).

White chocolate cake – in the sponges, replace the dark chocolate with white chocolate and reduce the butter to 160g (for best results, melt the white chocolate and butter separately), reduce the sugar to 150g, increase the gluten-free flour blend to 240g, increase the almond flour to 120g, and omit the cocoa powder. In the buttercream, replace the dark chocolate with white chocolate and omit the cocoa powder.

From Baked To Perfection: Delicious Gluten-Free Recipes, With A Pinch Of Science by Katarina Cermelj (£22, Bloomsbury), out now

Classic gluten-free baking recipes, from chocolate cake to blueberry muffins