Preheat oven to 350 degrees. Spray bottom and sides of 9-inch cheesecake pan lightly with nonstick cooking spray. Set aside.
Place Oreo cookies in a food processor and pulse a few times until you have fine crumbs. Place crumbs in a medium bowl. Add the melted butter and mix with a fork until well combined.
Place crumbs in the bottom of your prepared pan. Pack the crumbs down with your fingers. Bake crust for 9-10 minutes. Remove from oven.
In a medium bowl, whisk together flour, baking powder and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter and brown sugar on medium-high speed until light and fluffy. Turn the mixer to low and add the eggs, one at a time until well combined. Add the vanilla and continue to mix until incorporated. Slowly add the dry ingredients to the wet ingredients and mix just until combined.
Spread the mixture evenly on top of the Oreo cookie crust, smoothing the top. Top with broken Oreo cookie pieces. Bake until edges are lightly browned and toothpick inserted in middle of blondies comes out with just a few crumbs, about 35- 40 minutes. Begin checking at 35 minutes. Don't over bake.
Let blondies cool at least one hour and up to two before cutting into wedges or squares. Serve with vanilla ice cream, if desired.