For The Cupcakes, line the cupcake pan cavities with parchment paper and preheat the oven to 350F.
Sift all dry ingredients and set them aside.
1½ cups All-purpose flour, 1 teaspoon Baking powder, ½ teaspoon Baking soda, ¼ teaspoon Salt
Use the stand or hand mixer to beat the sugar and oil.
1 cup Sugar, ⅓ cup Oil
Add the egg and vanilla extract and mix until the eggs are incorporated.
1 Egg, 1 tablespoon Vanilla extract
Mix the buttermilk and sour cream separately and add to the batter. Sift in the dry ingredients and use a rubber spatula to fold them gently.
½ cup Buttermilk, ½ cup Sour cream
Crush about ten Oreo cookies using a food processor or a rolling pin. Do not crush them to fine crumbs; we want the chunks to be no smaller than a pea. Add the crushed cookies to the batter and gently mix the batter.
10 Oreos
Scoop the batter into the lined cupcake pan and fill the liners only to ⅔ of the way. Bake them for 15-18 minutes, and let them cool completely before frosting.
How To Make The Frosting
Be sure to use the room temperature butter. Using the whisk attachment, beat the butter for about 10 minutes. Yes, 10 minutes. This makes the butter smooth, creamy, and light. Stop the mixer and scrape the sides and bottom of the bowl to incorporate all the butter. There should not be any yellow butter in the bottom of the pan.
1 cup Butter
Add the powdered sugar in ¼ cup at a time and mix well after each addition. Add the vanilla extract and mix well. The buttercream should be smooth, creamy, and spreadable.