In a small pot melt butter and chocolate on low heat.

Whip sugar and eggs in a bowl until creamy, add cocoa and baking powder.

Carefully add flour.

Then add chocolate-butter-mix and the sour cream and stir well.

Grease a baking tray with butter, fill in dough and bake for 50-60 minutes at 180°C.

Whilst baking heat the cream and the chocolate in a small pot. Let melt while stiring constantly!

When your cake has cooled a bit, spread with the melted topping and cool in the fridge so the topping can get hard.