Preheat the oven to moderate, 180C/Gas 4-5
Grease two deep 22cm round cake tins and line bases with baking parchment
Beat butter, sugar and egg yolks in medium bowl with electric mixer until light and fluffy
Using a wooden spoon, stir in combined sifted flour and cocoa, then combined buttermilk and sour cream
Divide mixture evenly between prepared tins
Beat egg whites in a small owl with electric mixer until soft peaks form; gradually add extra sugar, 1 tablespoon at a time, beating until sugar dissolves between additions
Divide meringue mixture evenly over cake mixture in tins; using metal spatula, spread meringue so cake mixture is completely covered; sprinkle nuts over the meringue on one of the cakes
Bake cakes in moderate oven for 10 minutes
Cover tins loosely with foil and bake about 20 minutes more
Discard foil; stand cakes in tins for 5 minutes then turn onto wire racks
Beat cream and icing sugar until firm peaks form
Place cake without almonds on serving plate; spread cream over top, sprinkle evenly with fruit and top with remaining cake
Sprinkle some icing sugar on top
12 servings