For the Sugar Cookies:
1. Preheat your oven to 400 degrees F. Pre two 8-inch round baking pans with nonstick spray, parchment paper and spray again. Set aside.
2. In the bowl of a stand mixer fitted with a paddle attachment cream the butter and sugar until light and fluffy, about 2 minutes.
3. Add the eggs and vanilla. Mix until incorporated.
4. With the mixer on low speed, add the flour, baking powder and salt. Mix until just incorporated.
5. Cover and refrigerate at least one hour.
6. Measure out the 10 ounces of dough for each of the two cake pans. Using your hands, push the dough out to the edge of the pan (doesn’t need to be touching, just try to create an even circle).
7. Bake the two large cookies for 7 to 8 minutes. It shouldn’t be golden brown. We want the cookie to come out still light in color so it’s nice and soft in the cake.
8. For the rest of the dough, roll the dough out to about ¼ inch thick. Use cookie cutters to cut shapes and place the cookie dough 1 inch apart on the baking sheet.
9. Freeze the cut dough for 10 minutes and then bake 5 to 7 minutes (time will depend on the size of your cookies).
10. Cool completely before frosting.
For the Cake:
1. Preheat your oven to 350 degrees. Spray three 8-inch round baking pans with nonstick spray, line the bottom of each pan with parchment paper and spray again. Set aside.
2. In a medium bowl or measuring cup, combine and stir the egg whites, whole egg and the vanilla. Set aside.
3. In a bowl of an electric mixer, fitted with a paddle attachment, combine the dry ingredients together on low speed for 30 seconds.
4. Add the butter one piece at a time, about every 10 seconds. Once all the butter is added, pour in the buttermilk and mix on low for about 1 minute, until the ingredients are incorporated.
5. Scrape down the sides of bowl and begin to add the egg mixture in 3 separate batches, mixing on medium-low until light and fluffy, about 2 minutes. Fold once or twice to ensure the batter at the bottom of the bowl is incorporated and mix for another 20 to 30 seconds.
6. Using a kitchen scale, divide batter evenly among your pans (about 15 ounces of batter in each pan), spreading evenly with a small offset palette knife.
7. Bake until a cake tester or toothpick comes out with a few crumbs when inserted into the center, about 20 to 25 minutes. Check cake at 20 minutes and then set the timer for 2 to 3 minute intervals if the cake needs to bake longer. You’re looking for a few moist crumbs to come out on the toothpick when inserted into the center of the cake.
8. Let the cake layers cool on racks for 10 minutes before inverting onto greased wire racks. Gently turn the cakes back up so the tops are up and cool completely.
9. Once the cakes are cooled completely, level the tops if needed.
10. Wrap each cake layer with plastic wrap and chill in freezer for at least an hour before using.
For the Vanilla Buttercream:
1. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed for about 2 minutes, until light and fluffy.
2. With the mixer on low speed, gradually add the powdered sugar, heavy cream, vanilla and salt.
3. Turn the mixer to medium-high speed and beat the frosting for an additional 5 minutes, until nearly white.
4. Before frosting or piping, mix the frosting by hand with a wooden spoon or spatula to push out the air pockets.
For the Boiled Milk Frosting:
1. In a medium saucepan, whisk together the flour and ½ cup of the milk until smooth.
2. Set over medium-high heat and let cook for 1 to 2 minutes or until slightly hot, stirring frequently.
3. Whisk in remaining milk and salt. Whisk constantly until the mixture has thickened to the consistency of unset pudding (this can take up to 10 minutes).
4. Remove from heat and pour the mixture into a shallow dish. Cover the surface of the mixture with plastic wrap.
5. Place in the refrigerator until cool at least an hour
6. When cool, the mixture will be thick like custard. If a film formed on top of the mixture, remove it from the bowl.
7. In a large bowl (or a bowl of a stand mixer) beat the butter and sugar together until fluffy. Add vanilla and mix well. Beat in cooled flour mixture one tablespoon at a time on medium-high speed. When all the flour mixture is added, beat on high speed until light and fluffy, about 6 minutes
8. Rub a little frosting between your fingers. If the sugar granulates remain, beat for 4 more minutes or until granulates cannot be detected with fingers.
1. Place the first vanilla cake layer, top side up, on a cake board. Spread about 3/4 cup of the vanilla buttercream over the cake layer. Top with one layer of the sugar cookie rounds, followed by about 3/4 cup of the boiled milk frosting.
2. Repeat step 1 for the second cake layer and cookie layer. Place the third cake layer, top side down, on top of the second layer of boiled milk frosting.
3. Apply a thin coat of the boiled milk frosting around the entire cake to lock in the crumbs. Freeze the cake for 10 mins.
4. After the crumb coat is set, apply the final coat of the boiled milk frosting.
5. To get an extra sharp edge and straight sides, you can place an acrylic disk or extra cake round on top of the crumb coat. Once the acrylic disk is in place, frost and smooth the sides of the cake. Freeze the cake for another 20 minutes. At this point, the frosting will be a bit more set and you'll run a knife under the acrylic disk to "cut" it off from the cake. You'll have a nice crisp edge. Fill in the top of your cake with more of the boiled milk frosting.
6. Use remaining cookie dough to create shaped cutout cookies to decorate the sides of your cake.