In a 1- to 2-quart pan over low heat, melt 6 tablespoons butter; let cool. In a bowl, with an electric mixer on medium speed, beat melted butter, 1/4 cup powdered sugar, and the egg until well blended. Stir in graham cracker crumbs, coconut, pecans, and cocoa powder.
Press dough evenly into a buttered and floured 8-inch square baking pan. Bake in a 350° oven until slightly darker, about 20 minutes. Let cool completely.
Meanwhile, in a bowl, with an electric mixer on medium speed, beat 1/2 cup (1/4 lb.) butter, remaining 2 cups powdered sugar, the milk, and the vanilla until smooth. Spread mixture evenly over cooled crust.
In a 1- to 2-quart pan over very low heat, stir remaining 2 tablespoons butter and the chocolate until melted. Spread over filling. Cover and chill until the filling is firm enough to cut neatly, at least 2 hours. Cut into 25 squares.
Note: Nutritional analysis is per bar.