Preheat the oven to 350℉/180℃. Prepare a 9x9 baking pan by lining with parchment paper and set aside.
In a large bowl, add slightly cooled melted butter and dark brown sugar.
1/2 cup butter, 2/3 cups light brown sugar
Add in egg and vanilla and continue whisking.
1 egg, 1 tbsp vanilla
Add in the flour, baking soda, and salt. Using a spatula, slowly fold until no dry streaks appear. The dough will be soft! Don't over-mix.
1 cup all-purpose flour, 1/4 tsp baking soda, 1/2 tsp salt
Toss in the Oreo pieces and mix in a few times.
1/2 cup Oreos
Transfer into the prepared pan and spread out evenly. Top off with additional Oreo pieces if desired.
Bake the blondies for 20-25 minutes or until the blondies have a light golden edge and a toothpick inserted in comes out with a few crumbs.
Cool the blondies before slicing. If you slice them while they are hot, they will fall apart.
Enjoy!