Make 3 separate batches of cookie dough. Instructions for ONE batch follows.
Combine the flour, baking soda, and salt in a small mixing bowl and set aside.
2 1/4 cups all purpose flour, 1 teaspoon baking soda, 1 teaspoon salt
In a large bowl, beat the butter, granulated sugar, brown sugar, and vanilla extract with a hand mixer or stand mixer.
1 cup unsalted butter, 3/4 cup granulated sugar, 3/4 cup brown sugar, 1 teaspoon pure vanilla extract
Add the eggs, one at a time, beating well after each addition.
2 large eggs
Slowly add in the flour mixture until combined. Stir in mini chocolate chips.
10 ounces semi-sweet mini chocolate chips
Weigh the dough then divide into 4 smaller batches. Form each smaller batch into a circle. Flatten between 2 pieces of wax paper or parchment paper, rolling until the rolling pin is hitting the mini chocolate chips.
Freeze circles, separated between sheets of wax paper or parchment, for 2 hours or up to a month.
Repeat for 2 more batches.
Making the Buttercream
Beat softened butter in the bowl of a stand mixer using the whisk attachment until light and fluffy.
1 cup unsalted butter
Add in powdered sugar. Mix slowly, gradually increasing the speed so that the powdered sugar stays in the mixing bowl.
4 1/2 cups powdered sugar
Beat in vanilla extract.
1 teaspoon pure vanilla extract
Add the heavy cream and whisk on high speed. Scrape down the sides of the bowl, beat until desired consistency is achieved (about 5 minutes).
3 Tablespoons heavy whipping cream
Repeat for 3 more batches.
Baking the Layers
Preheat oven to 375 F. Line an insulated baking sheet with parchment paper. I used 4 total, but if you only have 1 or 2 that’s fine as well.
Bake the cookie layers, one at a time, straight from freezer. Bake for 10-12 minutes, mine were good at 11.5 minutes.
As soon as you remove the cookie sheet from the oven, use the edge of the spatula to form the hot cookie into a 9-inch circle.
Slide parchment with cookie onto a cooling rack and cool completely.
Repeat for remaining cookie layers.
Frost and Assemble
Add a tablespoon of buttercream to the center of your cake plate. Place a cookie layer on the cake plate.
Spread 1 cup of the buttercream on top of the first cookie and spread almost to the edges. Pipe frosting around the cookie along the edge.
Place second cookie on top of that and repeat.
Place third cookie on top of that. Add a tablespoon of buttercream in the center of that cookie and place a cardboard cake circle on top of that. This keeps the cake circle from sliding.
Pipe buttercream on the edges of the cookie. Add a tablespoon of buttercream to the center of the cake circle.
Place fourth cookie on top and repeat the above process. You want a cake circle every three layers. This allows you to cut the cake into 3 layer wedges, then remove the cake circle to move down to the next tier.
IMPORTANT - you will need 3 batches of cookie dough (one listed above) and 4 batches of buttercream (one listed above). You will not be able to make 3 batches of cookie dough in one bowl, it's easiest to separate them and work in batches. The listed ingredients above are for ONE batch of cookie dough and ONE batch of frosting.
I prefer to make the buttercream when I’m getting ready to assemble the cake. I don’t like to refrigerate it because it starts to get hard to spread.