Cake.

Preheat oven to 325* and butter the bottoms of 4 9-inch cake pans and line with parchment.

Sift together the flour and baking soda. Cream the sugar and butter -- add eggs and vanilla to the butter mixture -- mix thoroughly. Add the dry ingredients in three parts -- alternating with the cold water -- mix completely -- Add the sour cream and melted chocolate. Divide the batter between the prepared pans. Bake for 30 to 40 minutes -- cool the cakes in their pans for 15 minutes -- the cakes will sink to half their height -- Remove from pans and cool completely.

Frosting.

Place chocolate in large mixing bowl. Heat the cream, sugar, and corn syrup just to boiling -- pour over the chopped chocolate -- slowly stir till smooth. Add vanilla and cool completely -- then add sour cream -- frost -- store covered at room temperature.