1 cup (2 sticks) unsalted butter, at room temperature
1 1/2 cups sugar
4 large egg whites
2 tablespoons clear imitation vanilla (I use McCormick's --see headnote)
6 tablespoons vegetable oil
2 1/2 cups cake flour (see headnote)
2 1/4 teaspoons baking powder
3/4 teaspoon salt
1 cup whole milk
2/3 cup plus 1 tablespoon sprinkles
1. Preheat oven to 350° F. Grease two 8-inch cake pans. Cut out circles of parchment paper and line the bottom of the pans. Lightly spray the parchment. *We used two 10-inch cake pans for ours. A bit shorter but still did the trick!
2. Mix together the butter and sugar with an electric mixer 'til fluffy. Add in the egg whites one at a time, mixing after each one. Mix in the vanilla and oil.
3. Whisk the flour, baking powder and salt together in a medium bowl. Have your mixer on low and add this to the butter mixture in three additions, alternating with the milk. Make sure your batter is smooth and fold in the 2/3 cup of sprinkles.
4. Divide the batter up into the two pans. Sprinkle the remaining tablespoon of the sprinkles atop the cake and bake until a toothpick inserted in the middle comes out clean. Check for doneness around 25 minutes.
5. Let the cakes cool for a few minutes in the pans and then flip them onto a cooling rack to cool completely before frosting.