Line a 13x9x2-inch baking pan with heavy foil, allowing foil to extend over sides of pan; grease and set aside.
In a medium saucepan combine chocolate pieces and peanut butter; heat and stir over low heat until melted. Stir in nuts. Spread 1/2 of the mixture (about 1-1/4 cups) in prepared pan. Transfer to refrigerator. Let remaining chocolate mixture stand at room temperature.
In another medium saucepan combine sugar, marshmallows, butter and evaporated milk. Cook and stir over medium heat until mixture comes to a boil; cook 5 minutes more, stirring constantly. Remove from heat. Stir in cherry or peanut butter pieces until melted. Cool 10 minutes. Carefully spread over chocolate layer in pan. Chill 20 minutes.
Carefully spread on remaining chocolate mixture. Cover and chill at least 1 hour. Lift from pan using foil. Cut into small pieces. Store in an airtight container in the refrigerator. Makes 120 pieces.