Butter two 10-inch round layer cake pans and dust them with cocoa.
Cream together the butter, granulated sugar, and brown sugar. Beat in the eggs, then melt the chocolate in a double boiler over simmering water and allow it to cool.
Sift together the flour, baking powder, baking soda, salt and cocoa. Add the vanilla to the buttermilk. Add the cooled melted chocolate to the eggs and butter. Then alternately mix in the dry ingredients and the buttermilk.
Fill your pans about half full with butter.
Bake in the preheated oven about 40 to 45 minutes.
