Heat the oven to 160C/140C fan/gas 3. Butter a 23cm springform cake tin and line the base with baking parchment.

Melt the butter and chocolate in a medium heatproof bowl in the microwave or over a pan of simmering water.

Mix the coffee powder with 2 tbsp hot water until dissolved.

Stir the coffee into the chocolate and set aside to cool slightly.

Whisk the egg whites in a large bowl for 2 mins with an electric whisk until soft peaks form.

In another large bowl, whisk both the sugars, the vanilla and egg yolks together for 5-8 mins, or until pale and fluffy.

Sift the cocoa powder into the egg yolk mixture and mix gently to combine.

Stir the cooled chocolate into the egg yolk mixture, then gently fold through the egg whites until smooth.

Transfer to the tin and bake for 1 hr-1 hr 20 mins, or until a skewer inserted into the middle of the cake comes out clean. Leave to cool, remove from the tin and serve with fresh berries, if you like.