1. Preheat your oven to 350°F (175°C) and line an 8×8-inch baking dish with parchment paper, leaving some overhang for easy removal.
2. In a food processor, pulse the Oreo cookies until finely crushed. Combine the crushed Oreos with the melted butter in a bowl, mixing until well combined.
3. Press the Oreo mixture firmly into the bottom of the prepared baking dish to form an even crust. Set aside.
4. In a large bowl, beat together the peanut butter, granulated sugar, and brown sugar until creamy and smooth.
5. Add the egg and vanilla extract to the peanut butter mixture, beating until fully incorporated.
6. In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the peanut butter mixture, stirring until just combined. Fold in the chocolate chips, if using.
7. Spread the peanut butter mixture over the Oreo crust in the baking dish, smoothing the top with a spatula.
8. Bake for 20-25 minutes, or until the edges are just beginning to brown and a toothpick inserted into the center comes out mostly clean.
9. Allow the bars to cool completely in the pan on a wire rack before lifting them out using the parchment overhang. Cut into squares and enjoy!

It’s a simple process, but remember — patience is key! Letting the bars cool completely ensures they hold together beautifully when cut.