You don’t actually use a leavening agent with this Genoese sponge, as all the rising comes from the whisking. As soon as you add the melted butter to the mixture it begins to drop, so you must make sure your oven is hot and ready to take the sponge.
This recipe mixes the berries, but as an alternative I also like to have one blueberry layer, then strawberry, then raspberry and finally when you put the top layer on, dust it liberally with icing sugar.
If you get a hot metal skewer and place it on top of the icing sugar, it burns lines onto it and that creates a fantastic pattern on the top. Either way, it makes a great centrepiece to any celebration.
• 50g/13/4oz butter, melted, plus extra for greasing
• 250g/9oz plain flour, plus extra for dusting
• 250g/9oz caster sugar plus 1 tbsp
• 8 medium eggs
• 600ml/1pt pot double cream
• 400g/14oz punnet strawberries, halved
• 180g/6oz punnet blueberries
• 150g/51/2oz punnet raspberries
• icing sugar, to dust
1. Preheat the oven to 190°C/375°F/Gas 5. Brush 20cm/8in cake tins with melted butter, line the bases with baking paper, then dust well with flour, tipping out any excess. Set aside.
2. Put the sugar and eggs in a large heatproof bowl, then set it over a pan of barely simmering water. Whisk with an electric hand whisk for about 7 minutes or until the mixture is pale and has trebled in volume. Remove from the heat, then slowly pour in the butter, folding it in as you pour until it is completely mixed in.
3. Gently fold the flour and a pinch of salt into the egg mixture, then pour into your prepared cake tins. Cook for 25 minutes until the cake is golden and risen — a skewer pushed into the cake should come out clean. Allow the cakes to cool for a few minutes in the tin, then remove and cool completely on a wire rack.
4. Meanwhile, whip the cream until it just holds its shape. Whizz about a quarter of the strawberries with 1 tbsp sugar until smooth, then fold this purée through the cream so you get a ripple effect.
5. To assemble the cakes, cut each one in half horizontally. Put one sponge on a serving plate, spread a quarter of the cream mix on top, then dot a quarter of the blueberries and raspberries around the edge. Repeat this step two more times, put the last layer of cake on top (save a top half of cake for the top layer), spread the remaining cream over it, then put the blueberries and raspberries round the edge and pile the strawberries in the centre. Dust with icing sugar just before you serve.