1-First step: Get the pan and oven ready Preheat your oven to 350°F and grease a 9×13-inch baking pan. If you want easier removal, line the pan with parchment paper and leave a little overhang on the sides. This helps when lifting the cake out later, especially if you plan to serve it on a platter.

2-Second step: Mix the dry ingredients In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt. Whisking helps spread the leavening evenly through the flour, which supports a more even rise. Set this bowl aside so you can add it quickly when the wet ingredients are ready.

3-Third step: Cream the butter and sugar In a large bowl, beat the softened butter until creamy. Add the granulated sugar and beat again until the mixture looks light and well combined. This step adds air to the batter, which helps create a soft Oreo Sheet Cake with a tender bite.

4-Fourth step: Add the wet ingredients Mix in the egg whites, sour cream, and pure vanilla extract. Because the egg whites are at room temperature, they blend in more smoothly and help the batter stay light. Scrape the bowl as needed so everything mixes evenly.

5-Fifth step: Add the flour mixture and milk Turn the mixer to low speed and add the dry ingredients. Mix just until the flour starts to disappear, then pour in the whole milk. Keep mixing only until the batter looks smooth. Overmixing can make the cake dense, so stop as soon as the batter comes together.

6-Sixth step: Fold in the cookies Gently fold in the chopped chocolate sandwich cookies. Use about 1 and 1/4 cups, which is roughly 10 whole cookies, and stir just enough to spread them through the batter. Folding keeps the cookie pieces from breaking down too much and keeps the cake texture nice.

7-Seventh step: Bake the cake Pour the batter into the prepared pan and spread it into an even layer. Bake for 32 to 35 minutes, or until a toothpick inserted in the center comes out clean. If you use a different pan size, watch the cake closely since thinner pans may bake faster.

8-Eighth step: Cool completely Set the cake on a wire rack and let it cool all the way before frosting. This matters because warm cake can melt the whipped cream frosting and make the cookies soft too fast. If you are in a hurry, chill the cake briefly before frosting.

9-Ninth step: Make the frosting Beat the cream cheese until creamy in a clean bowl. Add the confectioners’ sugar and vanilla extract, then slowly pour in the cold heavy cream while beating. Keep mixing until the frosting turns thick and fluffy. This usually happens after a few minutes, and the cream should hold soft peaks.

10-Tenth step: Add the cookies and finish the cake Fold in the chopped chocolate sandwich cookies, about 1 cup or 8 whole cookies. Spread the frosting over the cooled cake in an even layer, then finish with mini or regular chocolate sandwich cookies on top if you want extra crunch and a pretty look. Slice and serve once the frosting is set.