To make the cupcakesPreheat your oven to 350°F and place your cupcake wrappers in your cupcake pan. 

In a large mixing bowl using a hand mixer or a stand mixer fitted with a paddle attachment, mix the cake mix and crushed Oreo cookies. Mix until the crushed cookies are coated with the dry cake mixture.

Add the eggs, water, milk, oil, and vanilla extract. Mix until all the ingredients are incorporated.

Scoop the batter evenly into the prepared cupcake pans using an ice cream scoop or a small measuring cup

Cook in your preheated oven for 14 to 17 minutes or until a toothpick comes out clean when inserted in the middle.

Let the cupcakes cool completely on a cooling rack before frosting.

To make the Cookies and Cream Frosting

In a large mixing bowl, cream the butter until soft, fluffy and light. 

Add powdered sugar, about ½ cup at a time, and mix with a hand mixer on low speed. Once the sugar is incorporated, continue to add portions of the powdered sugar until all the sugar is mixed in. 

Add in the finely crushed Oreo cookies and carefully mix until they’re completely incorporated.

If the cupcakes are completely cooled you can decorate them, if not you can place the frosting in the fridge covered with plastic wrap and decorate later. 

Pipe the frosting on top of the cupcakes using a piping bag fitted with a tip or a ziplock bag and cut corner.

Garnish the tops of cupcakes with a cookie broken in half.