3/4 cup (1.5 sticks or 170g) unsalted butter, melted and slightly cooled for 3 minutes
2 cups (400g) packed light or dark brown sugar
3/4 cup (194g) creamy peanut butter
2 large eggs + 1 extra egg yolk
1 Tablespoon pure vanilla extract (yes Tablespoon!)
2 cups (250g) all-purpose flour (spoon & leveled)
1 teaspoon baking powder
1 teaspoon salt
1 and 1/4 cups Reese’s Pieces
Directions
Preheat the oven to 350°F (177°C) and grease a 9×13 inch pan or line with aluminum foil or parchment paper, leaving an overhang on the sides to lift the finished blondies out (makes cutting easier!). Set aside.
In a large bowl, whisk the melted butter and brown sugar together until combined. Whisk in the peanut butter, then add the eggs, egg yolk, and vanilla. Whisk it all until completely combined.
Add the flour, baking powder, and salt. Fold the batter together using a rubber spatula. Batter is very thick. Finally, fold in the Reese’s Pieces. Spread evenly into prepared pan and sprinkle with a couple additional Reese’s Pieces on top for looks, if desired.
Bake for 30 minutes, then test the blondies with a toothpick. Insert it into the center of the pan. If it comes out with wet batter, the blondies are not done. If there are only a few moist crumbs, the blondies are done. Keep checking every 2 minutes until you have moist crumbs. My blondies take 30 minutes. They taste a little dry if you overbake!
Remove from the oven and place on a wire rack to cool completely before cutting into squares.
Cover and store leftover blondies at room temperature for up to 1 week.