I have so much respect for Christina Tosi! The Milk Bar is my favorite place in all of NYC, and everything on the menu is worth a try. This recipe is from the Milk Bar's first cookbook, which you should totally check out! The recipes are all awesome and unique, and it's a great read from cover to cover. This cake is quite sweet, but undeniably delicious! If you want to make the cake like I did, just divide the batter in half and bake in two 6" cake pans. Make 1.5 times the frosting recipe below, and assemble as you would a normal layer cake. Otherwise, make sure you stock up on all the tools you will need, like acetate strips and a 6" cake ring.
Preheat oven to 350°. Line a 13x9" rimmed baking sheet with parchment paper and coat with nonstick spray or shortening. Set aside.
In a large bowl, whisk together the flour, baking powder, salt, and ¼ cup of the sprinkles.
In a medium bowl, combine the buttermilk, oil, and vanilla.
In the bowl of an electric mixer, beat the granulated sugar, shortening, butter, and light brown sugar until light and fluffy, about 4 minutes. Add eggs, one at a time, beating well to blend after each addition. It is important to occasionally scrape down the sides and bottom of bowl after each addition as well.
Continue to beat mixture, scraping down sides and bottom of bowl every once in awhile, until almost doubled in volume and very light, airy, and pale yellow. This should take about 4 minutes.
Decrease the speed of the mixer to low, and slowly pour in the buttermilk mixture until incorporated. Add dry ingredients all at once, and beat until just combined - about 1 minute.
Scrape batter into prepared pan and smooth the top with an offset spatula. Sprinkle with the remaining 2 Tbsp sprinkles.
Bake in the preheated oven until the cake is light golden brown, the center springs back when gently pressed, and a tester inserted into the center comes out with a few moist crumbs attached, 30–35 minutes.
Remove cake from oven and cool on a wire rack.
Make the Crumbs:
Decrease the oven temp to 300°. Line a rimmed baking sheet with parchment paper (do not grease it) and set aside.
In a medium bowl, combine the flour, granulated sugar, light brown sugar, sprinkles, baking powder, and salt. Add the oil and the vanilla, and, using your hands, mix until no dry spots remain and large clumps form when mixture is pressed together. As though you were making a crumble topping, break mixture up into clusters (some small, some large) and spread onto prepared baking sheet. Bake, stirring occasionally, until the rumble is light golden brown and crunchy, 10–12 minutes (it will firm up as it cools). Let cool completely on a wire rack.
Make the Cake Soak
This one is easy - combine the milk and the vanilla.
Make the Frosting
Combine the butter, shortening, and cream cheese in the bowl of your stand mixer which has been fitted with the paddle attachment. Beat on medium-high until mixture is smooth and fluffy, 2–3 minutes. Scrape down sides of bowl and slowly stream in corn syrup and 1 Tbsp. vanilla. Beat until mixture is silky smooth and glossy white, about 3 minutes.
Scrape down sides of bowl and, with mixer on low, add powdered sugar, salt, baking powder, and citric acid until just combined. Increase speed to medium-high and beat until you have a brilliant stark white, beautifully smooth frosting, about 4 minutes (it should look just like it came out of a plastic tub at the grocery store!).
Assemble the cake
Place a silicone baking mat or piece of parchment on a counter. Invert cake onto mat, then peel off parchment. Use a 6" cake ring to punch out two 6" rounds from cake, or use a 6" springform pan to trace out 2 rounds, cutting with a paring knife. Do not throw away scraps - these two rounds are your top 2 cake layers, and the remaining cake will be smashed into the bottom layer.
Line a sheet pan with a clean piece of parchment. Place a clean 6" cake ring in the center of the pan. Use 1 acetate strip to line inside of cake ring. Place the leftover cake scraps somewhat evenly inside ring, and use the back of your hand to press scraps together into a flat, even layer. Trust me - it will stay together!
Generously moisten this layer with some of the cake soak. Brush it on with a pastry brush.
Use the back of a spoon to spread about 3 Tbsp. frosting evenly over cake. Sprinkle ⅔ cup of the crumbs evenly over frosting, and press them in place. Use the back of a spoon to spread another 3 Tbsp frosting as evenly as possible over crumbs.
With your index finger, gently tuck second acetate strip between cake ring and the top ¼" of the first acetate strip, so that you have a clear ring of acetate 5–6" tall—high enough to support the height of the finished cake. Top the previous layers with another round of cake. Brush layer with remaining milk mixture and repeat frosting-crumb layering process.
Top the cake with the remaining cake. Cover top of cake with the remaining frosting, using an offset spatula to form decorative swirls, Top with the remaining crumbs.
Transfer the finished cake to the freezer and freeze for at least 3 hours to set cake and filling.
At least 3 hours before serving, remove cake from freezer and, using your fingers and thumbs, pop cake out of cake ring. Gently peel off acetate and transfer the cake to a platter or cake stand. Defrost in fridge at least 3 hours before serving.
Recipe by Whisk Kid at https://whisk-kid.com/2015/07/celebration-momofuku-milk-bar-birthday-cake/