1. For crust, line a 13x9x2-inch baking pan with foil, extending edges over sides. Stir together graham cracker crumbs, nuts, coconut, the 1/2 cup sugar, the cocoa powder, 3/4 cup melted butter, egg, and 1 teaspoon vanilla in a large bowl until well combined. Press into prepared pan. Chill until firm, 1 hour.
2. For Creme de Menthe Layer, beat together 2 cups sugar, 1/2 cup melted butter, the creme de menthe, and 1/2 teaspoon vanilla in a large mixer bowl on medium speed until smooth. Spread evenly over crust. Chill 30 minutes, until firm.
3. For Chocolate Layer, combine the chocolate and 1/2 cup butter in a small bowl. Spread evenly over the Creme de Menthe Layer. Refrigerate bars 1 hour or until chocolate sets. Lift bars out of pan. Peel off foil and cut into 1-inch squares. Decorate as desired. Makes 6 dozen bars.