Preheat oven to 350 degrees. Liberally spray five 6-inch cake pans with nonstick cooking spray.

In a medium bowl, whisk together cake flour, almond flour, baking powder, and salt until combined. Set aside.

Combine milk and Amaretto. Set aside.

In stand mixer or another medium bowl, cream together butter and sugar on medium=high speed until pale and fluffy, about 3 minutes.

Reduce mixer speed to medium-low and add eggs one at a time, fully mixing each egg before adding the next. Add vanilla after all eggs are incorporated.

Add one-third of flour mixture into stand mixer on medium speed and blend to fully incorporate.

Add one-half of milk/Amaretto mixture and continue mixing to fully incorporate. Milk mixture may appear to slightly separate the butter; mixing will take care of this.

Continue to alternate adding one-third flour mixture, remaining half of milk/Amaretto mixture, and final one-third of flour mixture, fully combining before adding the next mixture, to form a smooth sticky batter.

Evenly divide cake batter among five baking pans. (Or three, if you are making an 8-inch cake).

For best results, use a kitchen scale to weight the batter for layers that bake more evenly and flat on top. The Evenbake cake strips wrapped around 8-inch cake pans works miracles for layers that come out of the oven flat! Unfortunately the strips are too large to be effective for the 6-inch pans.

If making an ombre layer cake, add increasing amounts of food coloring to each cake pan. (See my tutorial on making on ombre layer cake for full details)

Bake on top rack of oven for 28-30 minutes or until a toothpick inserted in the center comes out clean.

Cool in pans on a wire rack for 10 minutes, then invert and remove from pans to cool completely before trimming and brushing with amaretto simple syrup.

Add water and granulated sugar to a small pot on the stovetop. Bring to a boil, then reduce heat and simmer 2 minutes, stirring constantly.

Remove from heat and stir in Amaretto. Cool completely.

While syrup is cooling, trim tops of cake layers slightly so cakes are even and flat. Remove all "crust" to allow better absorption of the amaretto syrup. This keeps the cake moist and adds extra almond flavor.

Use a silicone brush to liberally brush each cake layer with amaretto syrup. Layers should appear moistened and shiny.

Place parchment paper between cake layers and freeze at least 30 minutes before assembling the cake layers with the ganache filling.

Place roughly chopped white chocolate (or white chocolate chips) into heat-proof bowl. In a small pot on the stovetop, heat heavy cream and Amaretto liqueur together until just boiling.

Remove from heat and pour cream mixture over the chocolate. Leave to stand for 5 minutes, then stir or whisk briskly until smooth.

Add softened butter and stir again until butter is fully melted and combined and the ganache is smooth.

Allow the ganache to cool until it is thickened (I placed mine in the freezer for 30 minutes to expedite the thickening.)

Remove the cake layers from the freezer and discard the parchment paper between layers. Place bottom cake layer onto parchment paper on a cardboard cake circle, and then pour 1/4 cup ganache onto layer.

Allow ganache to spread to cake edges; dripping down the sides is inevitable depending on the thickness of your ganache.

Add next cake layer and repeat. Do not press cake layer down; allow them to rest lightly on top of one another.

Repeat until cake is stacked with 1/4 cup ganache between each layer. Use 1/4 cup ganache on top of cake; set aside remaining ganache (this will be used for the final topping).

If cake layers are sliding askew instead of staying in place (the ganache is thinner than frosting, especially when warm), use wooden skewers to secure cake layers evenly in place.

Return cake to freezer for at least 1 hour, until ganache is thickened to a solid.

In stand mixer (with clean bowl), cream together butter with 1/4 cup heavy whipping cream.

Add powdered sugar 1/2 cup at a time, until 4 cups are incorporated. Mixture will be stiff.

Add 2 tablespoons of Amaretto and continue to mix. If frosting is still too stiff, add up to 3 tablespoons additional heavy cream until desired consistency is achieved. I like my frosting fluffy and soft because I find easiest to work with, so my recipe ended up using 1/4 cup + 3 tablespoons whipping cream in total.

Remove the ganache-covered cake from the freezer and remove skewers if necessary. Cake will be frozen in place and layers will no longer slip.

Use angled spatula to apply a thin crumb coating to sides of cake.

Apply thicker crumb coating to top of cake. Don't worry if frosting mixes with ganache. You'll cover the top with an additional layer of frosting. Just apply enough frosting to coat entire top and sides smoothly.

Return to freezer for 15 minutes. Tint remaining frosting with food coloring to achieve desired color. I used approximately 1/4 tsp Americolor Soft Gel Electric Purple for 3 cups of frosting.

Use spatula to frost sides of cake and smooth with icing smoother, wiping excess frosting from smoother in between passes. You may need to add additional frosting and smooth several times to achieve the frosting coverage and appearance desired.

To add sprinkles, apply with your hands, flat palm to gently push the sprinkles into the frosting.

Rotate cake and continue pressing sprinkles into frosting until desired coverage is achieved. Gently brush off excess sprinkles and reapply as needed.

Add 1/3 cup frosting to a piping bag outfitted with a star tip. (If you're frosting the cake in color, you may want to add additional food coloring to deepen the color of this frosting for contrast.) Pipe stars around the perimeter of the cake, making sure stars touch and do not leave gaps. This will act as a barrier to contain the final ganache.

If desired, tint remaining ganache. Ganache may need to be microwaved for 10 seconds to return it to a more pourable consistency. Pour ganache over the top of the cake and allow it to spread to the frosting stars.

Sprinkle the ganache liberally with additional sprinkles and pipe a few frosting swirls if desired.

Chill cake in refrigerator at least 30 minutes to allow buttercream to crust and ganache to set. Store cake in fridge until ready to serve. For best consistency, return cake to room temperature before serving.

Enjoy! Eating with silverware entirely optional.