2-15.25ounceboxes Funfetti Cake MixPrepare according to package instructions and bake in a half sheet pan
For the birthday cake soak:
For the birthday cake frosting:
3sticks unsalted butter24 tablespoons
3 1/2cupsconfectioners' sugar
For the birthday cake crumb:
3tablespoonslight brown sugar
1 1/2cupscake flour
1/2cupgrape seed oil
For the cake soak:
Whisk together the milk and vanilla in a small bowl. Set aside
For the frosting:
Combine the butter and cream cheese in the bowl of a stand mixer fitted with the paddle attachment and beat on medium-high for 2 to 3 minutes until the mixture is smooth and fluffy. Scrape down the sides of the bowl.
With the mixer on low, stream in the corn syrup and vanilla. Turn the mixer up to medium-high and beat for 2 to 3 minutes, until the mixture is smooth. Scrape down the sides of the bowl.
Slowly add the confectioners’ sugar, salt, and baking powder and mix on low speed just to incorporate them into the batter. Turn the speed up to medium-high and beat for 2 to 3 minutes, until you have a smooth frosting. Use the frosting immediately, or store it in an airtight container in the fridge for up to 1 week.
For the cake crumbles:
Preheat the oven to 300°.
Combine the sugars, flour, baking powder, salt, and sprinkles in the bowl of a stand mixer fitted with the paddle attachment and mix on low speed until well combined.
Slowly add the oil and vanilla and mix again to combine. Mix until small clusters begin to form.
Bake for 15 minutes at 300°.
Allow the crumbs cool completely before using in a recipe Stored in an airtight container, the crumbs will last for 1 week at room temperature or 1 month in the fridge or freezer.
To assemble the cake:
Lay a piece of parchment on the counter. Turn the cake onto it and peel off the parchment or silpat from the bottom of the cake. Use an 8 inch cake ring to stamp out 2 circles from the cake. These will be your top 2 cake layers. the remaining cake scraps will come together to make the bottom layer of the cake.
layer 1, the bottom
Clean the cake ring and place it in the center of a sheet pan lined with clean parchment or a silpat. Use 1 strip of parchment (4 inches wide x 24 inches long) to line the inside of the cake ring.
Place the cake scraps together inside the ring and use the back of your hand to press the scraps together into a flat even layer.
Dip a pastry brush in the cake soak and brush the soak over the cake scraps.
Use the back of a spoon to spread one-fifth of the frosting in an even layer over the cake.
Sprinkle one-third of the birthday crumbs evenly over the frosting. Use the back of your hand to press them in place.
Use the back of a spoon to spread a second fifth of the birthday cake frosting as evenly as possible over the crumbs.
layer 2, the middle
With your index finger, gently tuck the second strip of parchment (same size) between the cake ring and the top ¼ inch of the first strip of acetate, so that you have a clear ring of acetate 5 to 6 inches tall – high enough to support the height of the finished cake. Set a cake round on top of the frosting, and repeat the process for layer 1 (if 1 of your 2 cake rounds is uglier than the other, use it here in the middle and save the prettier one for the top).
layer 3, the top
Place the remaining cake round into the frosting. Cover the top of the cake with the remaining frosting. Garnish the frosting with the remaining birthday crumbs.
Transfer the sheet pan to the freezer and freeze for a minimum of 12 hours to set the cake and filling. The cake will keep in the freezer for up to 2 weeks.
At least 3 hours before you are ready to serve the cake, pull the sheet pan out of the freezer and, using your fingers and thumbs, pop the cake out of the cake ring. Gently peel off the parchment, and transfer the cake to a platter or cake stand. Allow it defrost in the fridge for a minimum of 3 hours (wrapped well in plastic, the cake can be refrigerated for up to 5 days).