Cooking spray
2 (15.25-oz.) boxed chocolate cake mix, plus ingredients called for on back of box
2 1/2 c. (5 sticks) butter, softened
8 c. powdered sugar
2 tbsp. heavy cream
1 tbsp. pure vanilla extract
1/4 tsp. kosher salt
Green food coloring
Sprinkles
Step 1
Preheat oven to 350°F. Grease and line five 8” round cake pans. Make cake mixes according to package directions and divide evenly between prepared cake pans.
Step 2
Bake until a toothpick inserted in the middle comes out clean, 20 to 23 minutes. Let cool for 15 minutes, then invert onto a cooling rack to cool completely.
Step 3
Wrap cooled layers in plastic wrap and freeze for at least 30 minutes and up to 3 days.
Step 4
Meanwhile, make frosting: In a large bowl using a hand mixer or in the bowl of a stand mixer fitted with the paddle attachment, beat butter until no lumps remain. Add powdered sugar and beat on low speed until smooth. Add cream, vanilla, and salt and beat until combined. Add more cream, 1 tablespoon at a time as needed, until desired consistency is reached.
Step 5
Working one layer at a time, use a long serrated knife to level tops of frozen cakes as needed.
Step 6
Use a 7” round cake cutter to cut out a circle from one cake layer and place on a cake stand or serving plate. Top with a thin layer of frosting. Cut the next layer using a 6” round cutter and place on top. Frost with a thin layer of frosting. Repeat with a 5” and 4” cutter for the next two layers.
Step 7
From the fifth cake layer, cut out a 3”, 2 ½”, 2”, 1 ½”, and 1” circles. Stack circles on top of cake with frosting between each layer.
Step 8
Add about ⅓ of the remaining frosting into a piping bag with a large round tip and pipe frosting all around the cake. Smooth frosting with an offset spatula and shape into a cone. Place cake in refrigerator for 30 minutes to help set frosting and make the cake more stable.
Step 9
Divide remaining frosting equally among 3 bowls. Dye one bowl light green, the second bowl a couple shades darker, and the third bowl a dark green.
Step 10
To a piping bag with an open star tip, place the light green on one side of the bag, then add the medium shade to a second side, and the dark green to a third side.
Step 11
Starting at the bottom of the cake, pipe frosting onto cake, pulling away from cake slightly as you release. Turn the bag every so often so that the shades of green are rotating to create a more natural look. Decorate with sprinkles for ornaments.