Creating these Cookies and Cream Brownies is simple if you follow these steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking pan with cooking spray or line it with parchment paper.
2. Mix Wet Ingredients: In a large bowl, combine the melted butter and sugar. Stir until well blended. Add the eggs and vanilla extract, mixing until fully incorporated.
3. Combine Dry Ingredients: In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt.
4. Combine Mixtures: Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix.
5. Add Cookies: Fold in the crushed chocolate sandwich cookies and white chocolate chips (if using) until evenly distributed.
6. Pour Batter: Pour the brownie batter into the prepared baking pan, spreading it evenly.
7. Bake: Place the pan in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
8. Cool: Remove the brownies from the oven and let them cool in the pan for about 15-20 minutes. Then, transfer them to a wire rack to cool completely.
9. Cut and Serve: Once cooled, cut the brownies into squares and serve.

Following these steps will ensure that your Cookies and Cream Brownies turn out perfectly every time!