Decorate: Cake can be made up to one day ahead. Keep in an airtight container in the fridge. Decorate just before serving.
• 6 free-range eggs, at room temperature
• 350g dark cooking chocolate, chopped, melted, cooled
• 125g unsalted butter, chopped, melted, cooled
Invert base of a 22cm springform pan (base 20cm). Grease and line base and side with baking paper, extending paper 2cm above pan edge.
Beat eggs in a large bowl of an electric mixer on high speed for 8–10 minutes, or until thick and pale. Add melted chocolate and butter in three batches, folding until well combined.
Pour mixture into the prepared pan and smooth over the top.
Cook in a moderately slow oven (160°C) for about 40 minutes, or until a skewer inserted into centre comes out clean. Stand in pan for 10 minutes. Transfer to a wire rack to cool.
Serve chocolate cake with double cream, fresh raspberries and halved strawberries if desired.