Preheat the oven to 350°F and line 24 muffin cups with baking cups.
In a medium bowl, whisk together flour, baking powder and salt.
In a large bowl, cream together the sugar and the butter until light and fluffy. Beat in vanilla extract, then beat in the egg whites one at a time, making sure each is fully incorporated before adding the next.
Working in 4 or 5 additions, alternately add the flour mixture and the milk to the sugar mixture. Keep the mixer on low speed while you do this. When just combined, stir in the crushed Oreos.
Spoon batter evenly into muffin tins, filling each about 2/3 full.
Bake for 15-18 minutes at 350°F, until a toothpick comes out clean (a few chocolate cookie crumbs are fine, but not batter).
Cool completely on a wire rack before frosting.
Store in an airtight container if not serving the same day.
Note: If you only have a 12-cup muffin tin, the batter will not suffer from sitting around for a few minutes while the first batch bakes. Just be sure to let the pan cool completely before filling it up again.
Variation: To make plain vanilla cupcakes, simply omit the Oreos. You might end up with only about 18 cupcakes, but as long as you fill the tins about 2/3 full, the baking time will be the same.
Quick Vanilla Buttercream Frosting:
Combine all ingredients in a large bowl and beat, with an electric mixer, until frosting is creamy, 3-5 minutes.
Frost cupcakes with frosting using a butter knife or offset spatula. Add as much or as little frosting as desired. If making Oreo cupcakes, garnish with additional chunks of Oreo.