Melt ½ cup butter and 1 ounces chocolate over low heat until melted. Add 2 tablespoons heavy cream, sugar, 1 teaspoon vanilla, graham cracker crumbs, coconut, and chopped nuts and remove from heat. Pour into a lightly greased 9 inch by 9 inch pan and chill. While base is chilling, cream ¼ cup of butter in mixer. Add powdered sugar, 1 tablespoon heavy cream, and 1 teaspoon vanilla, and beat until smooth and creamy. Spread evenly over base in pan. Chill. Melt last 1-½ ounces chocolate and spread quickly on top of cream layer. Chill. Cut into small (about 2 inch) squares.