1 1/4 cups butter
1/2 cup cocoa powder
3 1/2 cups confectioners' sugar, sifted
1 egg, beaten
1 teaspoon vanilla extract
2 cups graham cracker crumbs
1/3 cup green creme de menthe
1 1/2 cups semisweet chocolate pieces
Combine 1/2 cup of butter and cocoa in saucepan over low heat and stir until blended. Remove from heat and add 1/2 cup confectioners sugar' sugar, egg and vanilla extract. Stir in graham cracker crumbs. Mix well and press mixture into the bottom of a 13 x 9-inch pan.
Melt 1/2 cup butter and pour into a small mixing bowl. Add creme de menthe and mix at low speed. While mixing, add remaining 3 cups confectioners' sugar until smooth. Spread this mixture over the first layer in the 13 x 9-inch pan. Refrigerate entire dish for one hour.
While the dish is chilling, combine 1/4 cup butter and chocolate pieces in a saucepan over low heat. Stir until melted. Remove pan from refrigerator and spread chocolate mixture over the mint layer. Return pan to the refrigerator for 2 hours.
Cut into small squares and store in refrigerator until ready to serve.