Preheat oven to 350°F and line 3 6-inch cake pans with parchment paper. Spray the lined pans with nonstick spray. Set aside.
In a medium bowl, whisk the flour, baking powder, and salt together. Set aside.
2⅓ cups all-purpose flour, 2¼ teaspoons baking powder, ¾ teaspoon kosher salt
Add the butter to the bowl of a stand mixer fitted with the paddle attachment and beat for 1 minute on medium speed. Add the sugar and beat on medium speed until light and fluffy, about 3 minutes.
1 cup unsalted butter, 1¾ cups granulated sugar
Add the eggs, one at a time, mixing well after each addition. Add the vanilla and mix until combined. Use a spatula to scrape the sides of the bowl as needed. The batter should be fluffy, not curdled, once the eggs are incorporated.
4 large eggs, 2 tablespoons pure vanilla extract
With the mixer on low speed, alternate adding the dry ingredients and milk in batches to evenly incorporate: add ⅓ of the dry, half of the milk, ⅓ of the dry, last half of the milk, and last ⅓ of the dry. Scrape down the sides of the bowl to ensure that all of the ingredients are well mixed.
1 cup whole milk
Fold in the crushed Oreos with a spatula.
12 Oreo cookies
Evenly divide the batter into prepared pans.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven. Let the cakes cool in the pans for 10 minutes before removing from the pans and completely cooling on a cooling rack.