Lunchbox Brownies

Lunchbox Brownies
Makes:Active Time:Total Time:
1, 8-inch square pan25 min55 min


For the brownie batter base

  • 8 tablespoons (1 stick) unsalted butter (110g), melted
  • 1 cup granulated sugar (200g)
  • ½ cup unsweetened cocoa powder (50g)
  • 2 large eggs
  • 1 teaspoon vanilla extract (4g)
  • ½ cup all-purpose flour (75g)
  • ½ teaspoon kosher salt (2g)
  • ¼ teaspoon baking powder (1g)

For the peanut butter swirl

  • 2 tablespoons unsalted butter, melted (30g)
  • ¼ cup powdered sugar (30g)
  • ⅓ cup smooth peanut butter (90g)
  • ¼ teaspoon kosher salt (1g)


  • Heat the oven to 325°F and grease an 8 inch-square baking dish. Line the pan with parchment paper so there is a 2 inch overhang on opposite sides. These will serve as handles to lift the brownies from the pan.
  • Whisk together the melted butter, sugar, and cocoa powder in a large mixing bowl. Add the eggs and vanilla and vigorously whisk to combine.
  • Combine the flour, salt, and baking powder in a separate bowl, then stir it into the chocolate mixture until just combined. Set aside.
  • Add the butter, powdered sugar, peanut butter, and salt to a small bowl and mix until smooth.
  • Use the back of a spoon or an offset spatula to spread half of the brownie batter evenly into the baking dish. (The batter will be very thick).
  • Spoon half of the peanut butter swirl in tablespoon-sized dollops on top of the brownie batter.
  • Top with the remaining brownie batter and spread evenly, then dollop the rest of the peanut butter filling on top.
  • Insert a skewer or butter knife all the way to the bottom of the pan and drag the edge through the peanut butter dollops to make swirls.
  • Bake for 30-35 minutes, until puffed and lightly browned on top. Do not overbake.
  • A toothpick inserted into the center should come out a little wet with lots of crumbs.
  • Cool completely, then use the parchment handles to lift them from the pan and transfer to a cutting board.
  • Cut into squares and serve.