1melt butter in a 4-quart saucepan sprayed with cooking spray. Add cocoa and stir until smooth. Add sugar, salt, milk and marshmallow crème. Bring mixture to a full boil; boil and constantly stir 5 minutes or until 226 on candy thermometer. Remove from heat and stir in vanilla. Cool 20 minutes. Beat with a wooden spoon until mixture loses its gloss. Blend in nuts.
2Spread into a 9x9 pan sprayed with cooking spray. Cool until set. Cut into 1" squares. Store in an air-tight container.