Preheat oven to 350°F. Grease three 9-inch cake pans.
Whisk flour, baking powder, baking soda, and salt together in a mixing bowl. Set aside.
Beat the butter on high speed until smooth and creamy (roughly 1 minute). Add the sugar and beat on high speed for 5 full minutes until creamed and smooth. On medium-high speed, add 1 whole egg at a time until each egg is mixed in. Then add vanilla extract.
Using a mixer on a low speed, add the dry ingredients slowly alternating with the buttermilk. The batter should be smooth but not overly mixed. Last, not most important add the sprinkles until evenly mixed.
Bake for 25 minutes or until the cakes are baked through. To make sure the cakes are baked through, insert a toothpick into the center of the cake. The toothpick will come out clean when done. Allow to fully cool off.
Using a mixer, beat the butter on medium speed until creamy (2 minutes). Using a mixer on low, add sugar, cream, and vanilla extract. Once mixed, increase to high speed and beat for 3 full minutes.
Place 1 cake layer on a serving plate. Evenly cover the top with frosting. Top with 2nd layer and evenly cover the top with frosting. Add the third layer and evenly spread frosting over the top and sides. Add more sprinkles if desired.
Serve.