Grease the cake tin, dust with a little flour and line with a baking parchment disc. Preheat the oven 190Cfan/gas 5.
Melt the chocolate and butter in a bowl set over a pan with simmering water. Do not let the water touch the bowl. Once the chocolate and butter has melted remove from the heat and cool for 5-10 minutes.
Whisk the eggs, sugar and vanilla extract in a free standing mixer with a balloon whisk attachment until thick and pale in colour, this will take approximately 4-5 minutes. Pour the melted chocolate mixture into the whisked eggs and stir.
Sift the flour and salt then fold into the chocolate mixture. Pour into the prepared tin and bake in the centre of the oven for 15-20 minutes. Cool in the tin.
Serve with cream and berries.