1 (14 oz.) can sweetened condensed milk
1 (12 oz.) pkg. semi-sweet chocolate chips
1 (1 oz.) sq. unsweetened chocolate (if desired)
1 1/2 c. chopped nuts (if desired)
1 tsp. vanilla

Butter square pan, 8 x 8 x 2 inch. Heat milk, chocolate chips, and unsweetened chocolate over low heat, stirring constantly, until chocolate is melted and mixture is smooth. Remove from heat. Stir in nuts and vanilla. Spread in pan. Cool in refrigerator.