Spoon frosting into large resealable food-storage plastic bag; partially seal bag. Cut off tiny corner of bag. Insert cut corner of bag into indentation in each cookie cup. Squeeze bag to fill opening, about 1 generous tablespoon per cookie cup. Place stem end of strawberry on each frosting-filled cookie cup, and press down slightly so frosting becomes a brim for hat. Pipe a small dab of frosting on tip of each strawberry for pom-pom. Serve immediately, or store loosely covered in refrigerator.