Preheat the oven to 350 degrees.

Grease three 6-inch (or whatever size you prefer) cake pans and set aside. 

For the cake, cream the butter, sugar, and vanilla together until pale. Add the egg whites and mix just until combined. In a separate bowl, sift flour, baking powder, baking soda and salt together. Dump half of the dry ingredients in the butter mixture and slowly combine while adding in the buttermilk. Dump in the rest of the dry ingredients and then slowly mix while adding in the whole milk. Fold in the sprinkles and pour equal amounts into the cake pans.

Bake for 22-25 minutes or until golden. Let cool slightly, remove cake from pans, and finish cooling on baking rack.

For the frosting, with a standing mixer, whisk butter, vanilla, and water together until pale, about 10 minutes. Turn off mixer and add powdered sugar, and whip again until combined. 

Slice each cake layer in half to make 6 smaller cake layers.

Place 1 cup of frosting in a bowl and add blue food coloring and mix well until you like the color. Place 2 cups of frosting in a second bowl and color with red food coloring. Leave the remaining frosting white.

Layer the frosting between the cakes with red and white frosting perspectively. Crumb coat the entire cake by spreading a very thin layer of frosting over the entire cake. It’s okay that the cake shows through. Refrigerate for 15 minutes to set the frosting and crumbs.

Frost the entire cake with the rest of the white frosting and refrigerate for another 10 minutes.

Place the white chocolate and half and half in the microwave for 30 seconds at a time, stirring between each 30-second session until smooth and fully melted. This should only take 90 seconds total. Continue to whisk with a fork for a few more minutes until the ganache is completely smooth. Add food coloring until completely red. 

Place colored chocolate in a piping bag or condiment bottle and slowly drizzle the chocolate around the top edge of the cake while alternating squeezing more or less chocolate on each drip. 

Using a Wilton 2D tip and the blue frosting, pipes stars around the edge of the cake. Garnish each of the blue stars with a gold dragée and place two sparklers (or more!) in the center of the cake. Light and enjoy!