Make and decorate cookies one day in advance. Prepare cookie dough following recipe directions. Use rolling pin to roll out 3/16 in. thick. Cut with tree cutter from set. Bake and cool cookies.
Prepare Color Flow icing following recipe directions. Tint green. Use tip 2 and full-strength green icing to outline tree. Use thinned green icing in a cut disposable bag to fill in tree. Immediately position jumbo nonpareils. Let dry overnight.
Make cupcakes. Prepare white batter following recipe directions. Tint portions of batter 1/3 red and 2/3 green.
Place two-tone insert in baking cup-lined muffin pan. Use a cut disposable decorating bag to fill center ring of insert 2/3 full with red batter. Use a cut disposable decorating bag to fill outer ring of insert 2/3 full with green batter. Remove insert and repeat until all cavities are filled. Remove insert. Bake and cool.
Decorate cupcakes. Prepare buttercream icing following recipe directions. Tint green. Use tip 1M and green buttercream icing to pipe a swirl on top of cupcakes. Position snowflake sprinkles. Insert tree cookie.