Directions

1. Melt 1 cup of mint chocolate chips with 1/2 cup butter in a large saucepan over very low heat, and stir to combine. Mix in the chocolate wafer crumbs, coconut, and walnuts, and press the mixture into the bottom of an 8x8-inch square pan. Chill until the crust is set, at least 30 minutes.
2. Place 1/4 cup of softened butter into a mixing bowl, and beat in confectioners' sugar, milk, custard powder, and peppermint extract until the filling is smooth and thick. Beat in green food coloring, 1 drop at a time, to reach desired green color. Spread the filling on the crust in a smooth layer; refrigerate until set, at least 30 minutes.
3. Melt together 3/4 cup of mint chocolate chips with 1 tablespoon butter in a small saucepan over very low heat, and stir to mix thoroughly. Allow the mixture to cool for several minutes, then spread on chilled mint filling layer. Return the dish to refrigerator, chill until set, at least 1 hour, and cut into squares to serve.