Preheat oven to 325 degrees. Prepare a 9 or 10 inch springform pan by spraying the bottom with a non-stick spray.
In a stand mixer, combine the cookie mix, egg and butter and mix until soft dough forms. This process took 3-5 minutes for it to turn into dough.
Stir in the ¼ cup holiday sprinkles by hand.
Press the cookie dough mixture into the bottom of your pan. Bake for 30-35 minutes, until the top is golden brown; don’t let it get too brown.
Cool completely and prepare the frosting.
In a stand mixer, cream the butter. Slowly start to add in the powdered sugar until it’s all added in. Mix in the heavy cream by tablespoons, adding one at a time, until the desired consistency is reached.
Frost the cooled cookie cake, top with some sprinkles and candies, then pipe along the sides and top with more candies. Cut and serve! Best stored in an airtight container on the countertop.