Step 1

Since both the cake layers and cake crumbs need to cool completely, I recommend making them the day before you want to make the cake.

Step 2

Preheat the oven to 350°F and lightly spray three 6 inch layer cake pans with pan spray.

Step 3

Whisk the cake flour, baking powder, and salt together in a large bowl.

Step 4

In a separate bowl, whisk the melted butter, sugar, brown sugar, eggs, and vanilla together until combined.

Step 5

Stir in about half of the flour mixture. Then stir in the buttermilk and the rest of the flour mixture and mix until fully combined. The batter will be thin. Gently fold in the rainbow sprinkles.

Step 6

Pour ⅓ of the batter into each cake pan (they will only be about half full).

Step 7

Bake at 350°F for 20-30 minutes or until a cake tester comes out clean.

Step 8

Place a cooling rack on top of each cake pan and invert. The pan should slide cleanly away.

Step 9

Let the cakes cool completely to room temperature before trimming.

Step 10

Once the cakes are fully cooled. Using a sharp bread knife, trim the cakes until the layers are even. Wrap each layer tightly in plastic wrap and place in the freezer overnight.

Step 11

Combine all of then ingredients and mix together until it begins to form small clusters.Spread evenly on a baking sheet lined with parchment paper.

Step 12

Bake at 300°F for about 15 minutes.

Step 13

Let cool completely before assembling the cake. Store in an airtight container at room temperature for up to 5 days.

Step 14

Cream together the softened cream cheese and butter until smooth. Add in the vanilla extract and salt.

Step 15

Add in the powdered sugar 1/4 cup at a time until fully combined.

Step 16

Beat the frosting on high for 4-5 minutes until lightly and fluffy.

Step 17

Mix together the milk soak and lightly brush 1/3 of the milk onto the bottom layer of your cake.

Step 18

Spoon about 1/3 of the frosting in a nice even layer over the cake. Sprinkle on about 1/3 of the cake crumbs evenly over the frosting and then top with your second cake layer and repeat.

Step 19

Add the third layer and then smooth a very light coating of frosting around the top and edges of the cake.

Step 20

Then put the assembled cake back in the freezer for about 30 minutes to an hour. This is called the crumb coat. It helps trap any crumbs in that thin layer of frosting so that your final layer of frosting is perfectly smooth. The crumb coat isn't always necessary when you're working with already frozen cake layers or if you want to do a semi-naked cake like the one pictured!

Step 21

Sprinkle the remaining cake crumbs and some extra rainbow sprinkles on the very top!