Preheat oven to 350 degrees

Line 9x9 pan with parchment paper - set aside

Melt butter in a large bowl in microwave for approx 25-40 seconds

Whisk in peanut butter & brown sugar until fully combined

Whisk in eggs

Switch to a large spatula or wooden spoon & stir in salt, flour & baking powder

Transfer half the batter to prepared pan & press into a thin, even layer

Top with Oreo cookies & sprinkle in white chocolate & peanut butter chips

Add remaining batter, pressing into a flat layer - it's okay for some of the Oreos to show though, just not all of them.

Bake 20 minutes - then (using hot pads) carefully cover pan with foil & bake an additional 15-18 minutes

Remove foil & bake another 5 minutes or until tops no longer look doughy

Let cool in pan until ready to serve