In a large saucepan, melt 1/2 cup butter. Remove from the heat; blend in sugar, cocoa, vanilla, egg, crumbs and coconut. Also add nuts if desired. Press into a 9-in. square pan. In a small bowl, cream 1/4 cup butter, pudding mix, milk and sugar. Spread over crumb layer; chill. Melt chocolate and 1 tablespoon butter; spread over pudding layer. Chill before cutting into bars.