Preheat oven to 180 C / Gas 4. Grease a 20cm cake tin and line with baking parchment.
In a mixing bowl, lightly beat the eggs then sift in the flour and cocoa. Mix in the vanilla extract and sugar. Beat with electric mixer for several minutes until a smooth mixture is formed. Let stand for 3 minutes then pour into the prepared cake tin.
Bake in the preheated oven for 40 minutes or until a skewer inserted into the centre comes out clean.
For the cream:
Meanwhile, whisk the double cream with the mascarpone cheese, sugar and vanilla extract until creamy and stiff peaks form. Cover and chill in the fridge.
Remove the cake from the oven and let cool for 5 minutes in the cake tin. Turn out onto a cooling rack and allow to cool completely before decorating.
Once cooled, cover with the mascarpone cream and then decorate with berries on top and serve.