Conventional method: In a double boiler, melt chips and milk. Stir until smooth. Add nuts and vanilla. Microwave method: Melt chocolate chips and milk on 50 percent power, 3 to 5 minutes. Stirring twice while microwaving and once at the end until smooth. Stir in nuts and vanilla. Pour into prepared pan and chill until set.

Pour 2-1/2 cups into a large bowl; stir in chocolate chips and walnuts (if you want ’em) until chips are melted. Pour into the prepared, square pan. Add the butterscotch chips to the remaining marshmallow mixture; stir until chips are melted. Pour over the chocolate layer and gently spread to cover. Refrigerate until firm.