01 -
Set your oven to 350°F. Use parchment paper to line a 10×15-inch jelly roll pan, letting the edges go up the sides. Spray the parchment with nonstick cooking spray. Leave it aside.
02 -
In a big bowl, mix together salt, cake flour, and baking powder. Set it aside for later.
03 -
Using a stand mixer and the paddle attachment, beat softened butter, sugar, and vanilla on high until fluffy and pale, about 5 minutes. Scrape the bowl’s sides as needed.
04 -
Lower the mixer speed. Pour in the egg whites, one at a time, making sure each one is well mixed before adding the next. Don’t forget to scrape down the sides.
05 -
Keep the mixer running slowly. Add half the milk, then ⅓ of the dry mix, followed by the rest of the milk, another ⅓ of the dry mix, and the last of the dry mix. Stop once everything is combined. Scrape the sides as needed.
06 -
Carefully fold in the chopped Oreo™ pieces.
07 -
Pour the batter into your prepared pan and bake for 30-32 minutes. A toothpick poked in the cake should come out mostly clean, with only a few crumbs. Let the cake cool completely in the pan on a wire rack.
08 -
In a stand mixer, whip the butter until creamy. Slowly add 2 cups of the powdered sugar. Pause to scrape the bowl if needed. Add the rest of the powdered sugar and mix for 2-3 minutes until it’s airy and smooth.
09 -
Add whole milk, one tablespoon at a time, until it reaches the consistency you prefer. Stir in 1 cup crumbled Oreo™ cookies, saving the rest for decor.
10 -
Spread the buttercream evenly over the cooled cake. Sprinkle the remaining Oreo™ crumbs on top.