Preheat oven to 350 degrees Fahrenheit.

Butter the inside of three 6-inch round cake pans then dust them with flour.

For easy removal of your cakes, insert rounds of parchment paper into the bottom of the cake pans.

Whisk together the milk and egg whites and set aside.

Combine the flour, baking powder, and salt, and stir with a fork. Set aside.

Using an electric hand mixer, beat the butter and sugar, for about 3-4 minutes, until light and fluffy.

Pour in the almond (or vanilla) extract and beat just to combine.

Add ⅓ of the dry ingredients to the butter mixture and beat on low speed just until blended.

Pour in half of the milk mixture and beat on medium speed until creamy.

Stir in another ⅓ of the dry ingredients.

Pour in the remaining milk mixture and beat on medium speed until incorporated.

Add the sour cream and beat until smooth and creamy.

Add the remaining flour and beat on low speed just until combined.

Equally divide your cake batter among the three cake pans.

Bake on the middle rack of the oven for 28-34 minutes until a toothpick inserted in the center comes out with just a few moist crumbs.

Remove the cakes from the oven and set the pans on a cooling rack.

Allow the cakes to cool for 10 minutes then remove the cakes from the pans and allow them to cool completely.

Beat the butter on medium-high speed for 3 minutes using a hand mixer.

Add the powdered sugar, almond (or clear vanilla) extract, and 2 tablespoons of the heavy whipping cream.

Beat on low until the powdered sugar is incorporated, then increase the mixer speed to medium-high and beat for 2-3 minutes until the frosting is really light and fluffy.

Add more cream, a little at a time, until your frosting is the desired consistency to frost your cake.

Level the tops of your cakes, removing the domed pieces.

If you used parchment paper to line your cake pans, be sure to peel the paper off the bottom of each of your cakes.

Set one cake on a 6-inch cake cardboard or cake plate.

Add a ½ inch layer of frosting on top of that cake.

Stack on a second cake, frost that layer, then add the final cake on top.

Add a crumb coat of frosting to the outside of the cake and freeze the cake for 20 minutes.

Remove the cake from the freezer and frost the top and sides of the cake, reserving about ½ cup of frosting for the decoration.

Freeze the frosted cake for about 30 minutes while you are making and cooling your chocolate ganache.

Place the chocolate in a heat-proof bowl.

In a small saucepan, heat heavy cream until just simmering.

Pour over chocolate and let stand for 5 minutes.

Add corn syrup and stir mixture until combined completely.

Let the ganache cool for 15-30 minutes, stirring often, until it’s slightly thickened but still pourable.

Remove the cake from the freezer and press sprinkles around the bottom edge.

Either spoon the chocolate ganache over the top of the cake, allowing drips to from from around the top edge, or pour the ganache into a squeeze bottle and pipe chocolate ganache drips around the top edge and over the top of the cake.

Pop the cake into the freezer for 10 minutes to allow the chocolate ganache to firm up.

Spoon the remaining frosting into a pastry bag that is fitted with a large open star tip.

Pipe large open stars around the top edge of the cake.

Sprinkle on some rainbow jimmies to add some color to the frosting stars.

Allow the cake to come to room temperature before serving.