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3 peanut butter swirl brownies stacked up on a plate.

Peanut Butter Swirl Brownies

Peanut Butter Swirl Brownies are the perfect union of rich, fudgy chocolate and creamy peanut butter. Each decadent bite is richly flavored while a sprinkle of roasted peanuts on top adds a delightful crunch. If you like Reese’s Peanut Butter Cups, this dessert is for you!

Yield: 9 brownies (1 square pan) 1x
Prep: 15 minutesCook: 25 minutesTotal: 40 minutes


  • 3 large eggs
  • 3/4 teaspoon vanilla extract
  • 6 tablespoons unsalted butter
  • 2/3 cup semi-sweet chocolate chips
  • 1 batch Homemade Brownie Mix (sub: one 18-ounce box of brownie mix)
  • 1/2 cup peanut butter chips (sub: chocolate chips or Reese’s pieces)
  • 1/2 cup peanut butter
  • 3 tablespoons chopped roasted peanuts

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  1. Prep: Preheat oven to 350°F. Grease a 9×9 metal pan* generously with butter/cooking spray, or line with parchment.
  2. Wet Ingredients: In a medium bowl, whisk together eggs and vanilla. In a microwave-safe bowl or glass measuring cup, melt the butter and chocolate chips together in short 10-20 second bursts until smooth, stirring frequently. Be careful not to let the mixture get too hot. Let it partially cool for a few minutes.
  3. Combine: Stream the butter and chocolate mixture into the eggs and vanilla while whisking. Once smooth, add the brownie mix and fold in with a spatula until almost combined. Add the peanut butter chips and continue to fold the batter until no flour is visible (but do not over-mix). It will be quite thick. Spread the batter into prepared pan and spread until even.
  4. Swirl: Microwave the peanut butter until it has thinned slightly, about 15-20 seconds. Drop in dollops over the brownie batter and swirl into the surface by making figure-8 motions with a toothpick or offset spatula (some grooves in the batter are okay). Sprinkle evenly with the chopped peanuts.
  5. Bake: Bake for 22-27 minutes, rotating halfway. Check with a toothpick to ensure doneness. The brownies are done when there are only a few moist crumbs remaining on the toothpick and no wet batter is visible. Let cool before slicing.

Freeze For Later: The brownies can be frozen before or after they are sliced and kept in the freezer for up to 3 months. Store in an airtight container or ziploc bag after they are fully cooled. 

Prepare From Frozen: Take brownies out of the freezer and let thaw to room temperature.


  • If using our brownie mix recipe, be sure to mix it up in a separate bowl or shake it in a mason jar before adding to the wet ingredients.
  • *Changes for Various Pan Types and Sizes: We tested this recipe in various types and sizes of pans and here’s what our team discovered:
      • If using a 9×13 metal pan, bake for 15-20 minutes. 
      • If using a 9×13 metal pan for a double batch, bake for 35-40 minutes.
      • If using an 8×8 ceramic pan, bake for 35-40 minutes.
      • If using a 9×13 ceramic pan, bake for 22-27 minutes. 
      • If using a glass pan, this article says to try dropping the temperature from 350°F to 325°F and increasing the time anywhere from 5 to 15 minutes, depending on the volume of batter.⁠ (We haven’t tested this yet, but plan to soon!)
  • Creamy peanut butter (Jif or Skippy brand) is recommended, but you could also use crunchy peanut butter and omit the chopped peanuts on top (or do both if you want!). 
  • The peanut butter chips in the batter can be omitted or substituted for semi-sweet chocolate chips, or use half and half. Reese’s mini cups or pieces could also be added in and/or sprinkled on top!
  • Don’t over-mix the batter. This will cause the brownies to become tough.
  • The batter is very thick and if using parchment in the pan, it may slide around while you are trying to spread it. But, parchment may be easiest when removing the brownies from the pan because of how moist they are.
  • The less time spent spreading the batter in the pan, the better! Similar to over-mixing, this can create a tougher final product. Try to use longer strokes with your spatula.
  • A plastic knife will provide cleaner cuts than a metal knife when cutting the brownies.
  • Learn more about How to Freeze Brownies properly.
© Author: Polly Conner
Cuisine: American Method: Oven