1. Melt butter and peanut butter chips in large saucepan over very low heat, stirring often. Add cocoa; stir until smooth. Stir in sweetened condensed milk; stir constantly about 4 minutes or until mixture is thick and glossy. Remove from heat; stir in vanilla.
2. Refrigerate 2 hours or until firm enough to handle. Shape into 1-inch balls; roll in cocoa, nuts or graham cracker crumbs. Refrigerate until firm, about 1 hour. Store, covered, in refrigerator. About 3-1/2 dozen candies