Oreos, chocolate chips, and peanut butter cups are interspersed between a fudgy brownie layer and a chewy, butterscotch blondie layer.
For the Brownie Layer– 1/2 cup butter 113g– 1 cup brown sugar 220g– ½ cup dutch process cocoa 60g– 1/4 tsp fine sea salt– Small splash of vanilla– 2 large egg– 1/4 cup all purpose flour 31gOreodark chocolate chipFor the Blondie Layer– ½ cup unsalted butter 113g– 1 cup light brown sugar 210g– 1 large egg– ½ teaspoon fine sea salt– 2 teaspoons pure vanilla extract– 1 ½ cups all purpose flour 180gPeanut butter cup– flaky sea salt
Heat the oven to 350 F. Cover an 8- or 9-inch square pan with parchment paper (overhang on all sides).
STEP 1 .
I make the brownie and blondie layers together because the ingredients and steps are similar: Put butter in a heatproof bowl and melt.
Mix in sugar, salt, and vanilla. Whisk it well to make it smooth, then add the egg to the blondie bowl and the brownie bowl (the brownie batter will be lighter due to the extra egg).
Add flour to bowls and cocoa to brownie batter; whisk. Cover the pan with brownie batter.
Put 9 Oreo cookies in the brownie batter and press them down. Top with chocolate chips.
Add the peanut butter cups without pressing them into the blondie layer. Bake until center puffy and falling after rising 40 minutes.
If it overbrowns before puffing, foil it. Sprinkle flaky sea salt on the bars and cool before slicing.