Preheat the oven to 350℉/180℃. Grease an 8×8 inch square pan. For easy removal of the blondies, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set side.
Melt the butter. As it cools, prep and measure the rest of your ingredients.
1/2 cup butter
In a large bowl, whisk together the slightly cooled melted butter and white sugar until well combined. You may use a whisk, or an electric mixer.
3/4 cups white sugar
Add in peanut butter and continue whisking.
1/2 cup peanut butter
Add in egg, egg yolk, and vanilla. Continue to whisk until well combined.
1 egg, 1 egg yolk, 2 tbsp vanilla
Toss in the flour, baking powder, and salt. Once it is almost completely mixed in, add the crushed Oreos and continue mixing until no flour streaks appear and there is a soft dough.
1 cup all-purpose flour, 1/2 tsp baking powder, 1/2 tsp salt, 1/2 cup Oreos
Evenly press the dough into the prepared pan.
Gently press more broken Oreos and globs of peanut butter on top of the blondies. This is optional.
Bake for 24-27 minutes. Mine took exactly 27 minutes.
Cool, slice, and enjoy!