Remove wrappers from peppermint patties; break into pieces. Place candy and 2 to 3 teaspoons milk in 8-oz. mug. Microwave at HIGH (100%) 30 seconds; stir. If necessary, microwave at HIGH an additional 15 seconds at a time, stirring after each heating, until candy is melted and mixture is smooth when stirred.
Slowly stir in remaining milk. Microwave at HIGH 1 minute; stir. If necessary, microwave an additional 15 seconds at a time until the desired temperature is reached. Garnish with cocoa,if desired. Serve immediately.