For the rim, use a butter knife to add a ring of frosting around the rim.

Dip the rim into the sprinkles to coat.

For the shake, add ice cream, milk, and Christmas Tree cakes to a blender.

Blend until smooth. If needed, you can add extra milk to thin the shake, or ice cream to thicken it to your desired consistency.

Top the shake with cool whip, sprinkles, and a Christmas Tree cake.