Heat oven to 320F. Melt 2 cups of dark chocolate. Separately whisk butter and brown sugar until light and fluffy. Add eggs one at a time, add melted chocolate. Fold in flour mixed with baking powder. Pour into a 9 inch round pan. Bake for 1 hour until knife comes out clean - no longer than 90 minutes. For the filling, melt 3/4 cup chocolate with double cream. Let cool to thicken (if not thick then whip it). You can chop the cake into two layers and put this in the middle, or just on the top and sides.
makes 1 cake