In a large mixing bowl, combine nuts, marshmallows, crushed crumbs, and sugar. Mix well. In a sauce pan, melt chocolate in evaporated milk over low heat; stirring until thick and smooth. Remove from heat and add extract.
Reserve 1/2 cup (approx.) of chocolate mixture for icing. Add remainder to crumbs mixture. Stir until all crumbs are moistened. Turn into large 9 x 13 inch pan, greased with a small amount of butter. Spread remaining chocolate mixture on top. Cool and cut in squares. |