Meanwhile, prepare instant vanilla pudding using 1/4 cup less milk that recommended. Allow the pudding to set in the fridge for 5 minutes. Then whisk in one part Cool Whip to 2 parts pudding. It doesn't have to be exact. The Cool Whip makes the texture of the pudding so much more creamy.
Fill an icing bag with 1/2 the pudding, using a large hole icing tip. Fill each cupcake with the pudding until the tops of the cupcakes puff slightly.
Frost 21 cupcakes with green frosting & top with M&M's (or Smarties) & sprinkles. Frost 1 cupcake yellow with sprinkles and 2 with brown & top with chocolate sprinkles.Assemble Christmas Tree on a cake board wrapped with festive paper.
Store in the fridge (because of the pudding) until ready to serve.
