1 (12 oz.) pkg. semi-sweet chocolate chips
1 cube butter
1 lb. powdered sugar
2 eggs, at room temperature
1 tsp. vanilla

Melt chocolate and butter over low heat. In mixing bowl with electric beater, mix remaining ingredients. Add melted mixture to sugar and egg mix (plus 1 1/2 cups nuts, if desired). Mix with spoon until well blended. Pour into buttered 8x8 or 9x13 inch pan or dish. Refrigerate at least 2 hours. Cut and serve.