Place 1/3 cup mint chocolate morsels in a glass bowl, and microwave at HIGH 1 minute or until almost melted, stirring until smooth. Cool.
Add cream cheese to melted morsels; beat at medium speed with an electric mixer until smooth. Add 1 package powdered sugar, and beat until well blended. Spread mixture in an 8-inch square pan; cover and chill 8 hours.
Shape mixture into 1-inch balls, cover and freeze 3 to 4 hours.
Roll truffles in cocoa or powdered sugar.
Place 2 tablespoons chocolate morsels in a heavy-duty zip-top plastic bag seal. Submerge in hot water until chocolate melts. Snip a tiny hole in corner of bag; drizzle chocolate over truffles. Let stand at room temperature 30 minutes before serving.
Note: Freeze truffles in a single layer in an airtight container up to 1 month. Let stand at room temperature 1 hour before serving.