Preheat the oven to 350F and grease and line the bottoms 3 – 9" cake pans with parchment paper.

Whisk together the flour, baking powder, baking soda, and salt and set aside.

Using a hand or stand mixer, cream together the butter and sugar until light and fluffy mixing on medium high speed for 3-5 minutes.

With the mixer running on low, pour in the oil. Scrape down the bowl and give it another mix.

Mix in the eggs one at a time followed by the vanilla. Scrape down the bowl after every 2 eggs.

Mix in the sour cream.

With the buttermilk and dry ingredients, mix into the batter alternating between the two, starting and ending with the dry ingredients.

Take the bowl off the stand once the batter is combined. Fold in the sprinkles.

Pour into your cake pans and spread it even. For 9" cakes, bake for 30-35 minutes. For 8" cakes, bake for 35-40 minutes.

Allow the cakes to cool in the pans for 30 minutes, then run a knife around the edges and turn them out on to a cooling rack.

Mix the butter using a hand or stand mixer with the whisk attachment until smooth.

Mix in one cup of powdered sugar at a time, adding the vanilla and milk as it begins to thicken.

Level off the chilled cakes if needed.

Spread a thin layer of buttercream between each cake layer, then give the entire cake a thin crumb coat.

Frost the cake with the rest of the buttercream and decorate with extra sprinkles.