A subtly Spanish twist on a French classic. These simple desserts are perfect when you're entertaining - make them in advance and keep them in the fridge until you're ready to start. Then just create the crunchy topping and serve immediately.

• Preheat the oven to 200C\180C Fan\Gas Mark 6. Butter a 32cm x 23cm swiss roll tin and line with greaseproof paper.
• Whisk the egg yolks until they are thick and creamy then slowly beat in the cocoa powder and half of the sugar. In a separate bowl, with clean whisks, beat the egg whites until they form soft peaks then gradually add the remaining sugar mixed with the cream of tartar.
• Beat a spoonful of the egg white mix into the yolks to loosen, then gently fold the yolk mixture into the whites with a metal spoon until well combined. Pour into the prepared tin making sure it’s spread into the corners and bake for 15 minutes until it’s cooked through and springs back when you gently touch the centre.
• Cool for 5 minutes then turn out onto a large sheet of greaseproof paper dusted with cocoa powder. Gently peel off the grease proof paper it was cooked in, then roll it up in the new paper and leave it to cool on a wire rack.
• Put the chocolate and butter in a mixing bowl. Heat the cream in a pan until almost boiling, then pour over the chocolate, stir until smooth then chill in the fridge for 10 minutes until it firms up.
• Chop half of the strawberries into small pieces and stir into half the ganache. Unroll the sponge, spread with the strawberry ganache. Slice the remaining strawberries and spread them in a layer on top of the ganache. Re-roll the cake carefully so you don’t squeeze the filling out. Don’t worry if it cracks. Spread the remaining ganache over the cake and top with some additional strawberry slices, dust with a little icing sugar to serve.