Momofuku Milk Bar Cake

Birthday cake crumbs

100 grams granulated sugar
25 grams light brown sugar
90 grams cake and pastry flour
2 grams baking powder
2 grams salt
20 grams rainbow sprinkles
40 grams grapeseed oil
12 grams vanilla extract

Preheat the oven to 300°F. Line a baking sheet with a Silpat or a piece of parchment.
In the bowl of an electric mixer fitted with the paddle attachment, combine the sugars, flour, baking powder, salt, and sprinkles and mix them on low speed until they are evenly mixed.
Add the oil and the vanilla and continue beating the mixture until the ingredients clump and form small clusters.
Carefully spread the delicate clusters in a thin layer on the prepared baking sheet and bake them for about 20 minutes. They dry and harden as the cool into crispy crumbs. Let them cool completely before using them. By the time you’ve made the cake and frosting, they will be ready to be used anyways.

Birthday cake

Pam or vegetable oil for preparing the pan
245 grams cake and pastry flour
6 grams baking powder
3 grams salt
50 grams rainbow sprinkles
55 grams unsalted butter, room temperature
60 grams vegetable shortening
250 grams granulated sugar
50 grams light brown sugar
3 large eggs
110 grams buttermilk (made from skim milk and white vinegar)
65 grams grapeseed oil
8 grams vanilla extract
25 grams rainbow sprinkles

Preheat the oven to 350°F (use an oven thermometer to verify the temperature). Prepare a rimmed quarter sheet pan (mine is a 10-x15-inch pan with a 1-inch rim) by spraying it all over with Pam and then covering the base with a sheet of parchment. Set aside.
Whisk together the flour, baking powder, salt, and 50 grams of sprinkles in a small bowl. Set the dry ingredients aside for later.
In the bowl of an electric mixer fitted with the paddle attachment, cream together the butter, shortening, and the sugars on medium-high for 2 to 3 minutes, scraping down the bowl as needed.
Add the eggs (all at once) and then beat again on medium-high for another 2 to 3 minutes. Scrape down the bowl.
In a 1-cup measurer, weigh out the buttermilk, grapeseed oil, and vanilla. With the mixer on low, add the wet ingredients in a steady stream. Increase the mixer speed to medium-high and beat for another 4 to 6 minutes. The mixture will double in size almost, and will appear light and fluffy. There will be no trace of oil left.
With the mixer on low, add the dry ingredients, and mix for another minute or so until the ingredients are all combined.
Pour out the batter into the prepared sheet pan, spreading it out into an even layer. Sprinkle with the remaining 25 grams of rainbow sprinkles.
Bake for 30–35 minutes until the cake bounces back slightly when gently pressed in the corner. The center of the cake should no longer jiggle when the pan is shook. Cool the cake completely in the pan on a wire rack.

Birthday cake soak

55 grams milk (I used whole milk—3.25% fat)
4 grams vanilla extract

Whisk together the milk and vanilla in a small cup or bowl. Set aside for later.

Birthday cake frosting

200 grams powdered sugar
2 grams salt
Pinch baking powder
Pinch citric acid
115 grams unsalted butter, room temperature
50 grams vegetable shortening
55 grams cream cheese
25 grams glucose
18 grams clear corn syrup
12 grams vanilla extract

Whisk together the powdered sugar, salt, baking powder, and citric acid in a medium bowl. Set aside for later.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter, shortening, and the cream cheese for 2 to 3 minutes on medium-high until the mixture is smooth and fluffy. Be sure to scrape down the bowl periodically.
Add the glucose, corn syrup, and vanilla, and beat the mixture on medium-high again, for 2 to 3 minutes until it is silky smooth and a little glossy. Scrape down the bowl a few times.
Now add the whisked dry ingredients and incorporate them on low speed. Increase the mixer speed to medium–high and beat the frosting until it is creamy and fluffy, just like the kind that comes in a can.

Birthday cake assembly

1 batch birthday cake
1 batch birthday cake soak
1 batch birthday cake frosting
1 batch birthday cake crumbs
4 8-x3-inch strips of acetate
1 6-inch cake ring that is 3 inches high (or a springform ring)
1 8-inch square of parchment

Cut the sheet cake into two 6-inch circles plus two half-circles using your cake ring as a template. Use a spatula to gently loosen and lift (carefully!) the circles and set them aside.
Place the cake ring on a baking sheet lined with the 8-inch square of parchment. Line the inner rim of the ring with two pieces of acetate so that they overlap a little.
Fill the bottom of the ring with the two half circles of cake. Press them slightly so that they are even. If there are any holes, fill them with the rest of the cake scraps.
Brush half the birthday cake soak over the base of cake.
Spread about 100 mL (one-fifth) of the birthday cake frosting over the base layer. Then sprinkle with one-third of the birthday cake crumbs, pressing them gently into the frosting. Top with another 100 mL (another fifth) of the birthday cake frosting, carefully spreading it so that it is even, but without disturbing the crumbs.
Top with a full circle of cake, brush the rest of the cake soak over this layer, top with more frosting, cake crumbs, and another layer of frosting.
Squeeze in the other two strips of acetate between the inner rim of the ring and the first acetate strips (you are essentially making your cake ring taller at this point). Top with the last circle of cake. and the remaining frosting, spread evenly. Top with the remaining cake crumbs.
Freeze the cake as is for at least 12 hours to set everything and making the unmolding process much easier.
Three hours before serving, retrieve the pan from the freezer, and gently push the cake through the ring. Place it on a cake stand or cake plate. Now gently pull off the acetate ribbons.
Let the cake defrost in the fridge before serving. Cut neatly with a large chef’s knife.