Momofuku Milk Bar Birthday Cake

Ingredients
4 tablespoons butter
1/3 cup vegetable shortening
1 1/4 cups sugar
3 tablespoons tightly packed brown sugar
3 eggs
1/2 cup buttermilk
1/3 cup grapeseed oil
2 teaspoons clear vanilla extract (Wilton has a good one)
2 cups cake flour
1 1/2 teaspoons baking powder
3/4 teaspoons kosher salt
1/4 cup rainbow sprinkles plus 2 additional tablespoons
Preparation method