PREPARE brownie bites according to package directions. Cool on baking sheet for 2 minutes; remove to wire racks to cool completely.
LINE baking sheets with wax paper.
SORT out 2 tablespoons mint morsels and place in small, heavy-duty plastic bag for drizzle; set aside.
MICROWAVE remaining morsels and vegetable shortening in medium, uncovered, microwave-safe bowl on MEDIUM-HIGH (70%) power for 1 minute; STIR. The morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until smooth.
PLACE 5 cookies top-side down on top of melted chocolate. Using tongs, remove cookies from bowl, scrapping cookies against side of bowl to remove excess. Place cookies top-side-up on prepared baking sheets. Repeat with remaining cookies and chocolate.
MICROWAVE reserved mint morsels in bag on MEDIUM-HIGH (70%) power for 20 seconds; knead. Microwave at additional 10- to 15-second intervals, kneading until smooth. Cut tiny corner from bag. Drizzle quickly over cookies. Refrigerate for 15 minutes. Store cookies in covered container in refrigerator.