In a microwave, melt chocolate chips; stir until smooth. Spread the flat side of each kiss with a small amount of melted chocolate; Immediately attach each to a cookie.
Cut a small hole in the corner of a plastic bag; insert a small round tip. Fill with remaining melted chocolate. Pipe a stem onto each acorn. Place on waxed paper-line baking sheets; refrigerate until set. Store in airtight container.