8 oz (225 g) dark semisweet chocolate (40-50% cocoa)
2/3 cup (140 g) butter
1 cup (210 g) sugar
4 heaped tablespoons (1 dl) all-purpose flour
4 tablespoons unsweetened cocoa powder
1½ teaspoon baking powder or 1 teaspoon baking soda
1 teaspoon vanilla extract
4 tablespoons sour cream
Ingredients for frosting
2/3 cup (1.6 dl) heavy cream or whipping cream
9 oz (260 g) semisweet chocolate (40-50% cocoa)
Preheat oven to 180 °C/350 °F
Break the chocolate into small pieces and melt it with butter over hot water.
Beat the eggs with sugar, mix with flour, cocoa powder, baking powder and vanilla extract.
Slowly fold in the melted butter and chocolate and the sour cream.
Bake until a wooden pick inserted in center comes out clean, approximately 40 to 50 minutes
Cool the cake completely. When it has obtained room temperature place it in the refrigerator for at least 30 minutes before removing the cake from the tin (the cake is sticky and difficult to cut when it is warm!) Remove the crusted surface on the top of the cake, and cut in half, horizontally.
Heat 2/3 cup of heavy cream or whipping cream in a sauce pan.
Remove from heat, add 260g of finely chopped dark semisweet chocolate, stir until smooth, and let it cool until in thickens.
Use one 1/3 of the frosting between the two layers, 1/3 on top, and the rest around the cake. Put the cake into the fridge for one hour or more to harden the frosting.