Go Back
Layered brownie bars with a crackly chocolate top and gooey marshmallow and peanut butter center, cut into squares and served on a cutting board.
Summer Dempsey

Gooey Peanut Butter Brownies

Ultra gooey marshmallow peanut butter brownies made with a soft baked base and creamy layered filling—rich, easy, and perfect for crowd-pleasing desserts.
Print Recipe Pin Recipe
Prep Time 10 minutes
Cook Time 40 minutes
Cooling Time 1 hour
Total Time 1 hour 50 minutes
Servings: 9
Course: Dessert
Cuisine: American
Calories: 335

Ingredients
  

  • ¾ cup sweetened condensed milk divided
  • ¼ cup butter melted & cooled slightly
  • ¼ cup milk
  • 1 box brownie mix
  • 1 large egg white lightly beaten
  • Cooking spray
  • 7 oz marshmallow crème
  • ¾ cup peanut butter morsels

Equipment

  • Stand Mixer
  • 9x9 Non-Stick Pan

Method
 

  1. In stand mixer, combine ¼ cup of the sweetened condensed milk, melted butter, milk, brownie mix and egg white. The batter will be thick.
  2. Use Parchment paper AND no stick spray (spray Non-stick spray on top of the parchment paper) to prepare the 9x9-inch baking dish. Spread ⅔ of the brownie batter into the bottom of the pan (it helps to use a spatula sprayed with cooking spray). The layer will be thin.

Bake the base:
 Bake for 10 minutes at 350°F.

  1. In a medium bowl, stir together the remaining ½ cup sweetened condensed milk with the marshmallow crème and peanut butter morsels. Mix until smooth.
  2. Spread the marshmallow mixture evenly over the partially baked brownie layer. Carefully drop the remaining brownie batter by spoonfuls over the marshmallow layer. ( try to spread out the brownie batter at much possible)
  3. Optional step: swirl the top layer for a nicer look, being careful not to swirl the bottom layer.

Final bake: 
Return to the oven and bake for 35-45 minutes at 350°F, until the top looks set and slightly crackly.

  1. 
Let cool completely before cutting into squares. These are rich and gooey, so smaller portions work best!

Notes

 

  • Use parchment + spray together: This is key for clean removal—these brownies are very sticky and gooey.
  • Don’t overbake: The center should still be slightly soft when removed. They will set as they cool.
  • Layering tip: Drop the top batter in small spoonfuls instead of spreading—it’s much easier over the marshmallow layer.
  • Cool completely before cutting: For clean slices, let them fully set (you can even chill slightly).
  • Use a hot knife: Run a knife under hot water and wipe dry between cuts for bakery-style squares.
  • Swirling is optional: It adds a pretty finish, but skipping it won’t affect flavor or texture.
  • Pan size matters: A 9x9 pan keeps these thick and gooey—using a larger pan will make them thinner and bake faster.