Peanut-Butter Swirl Brownies

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These are our most decadent brownies—and they're not to be missed.

Peanut butter swirl brownies
Credit:

Rachel Marek

Yield:
Makes 9 large or 16 small squares

Peanut butter and chocolate is a sublime combination; sweet and salty, rich and decadent. Even if you're in the camp who thinks nothing is better than a chocolate brownie, you should make this artfully swirled version of your favorite treat where dollops of peanut butter filling are spooned onto brownie batter. Pulling a knife back and forth through both batters results in a marbleized look.

Like many brownies, no mixer is needed for this recipe, just two bowls (and perhaps some self-restraint so you don't eat more of these peanut-butter swirl brownies than you should!). Our advice is to make these brownies when you have company coming or are going to a potluck, so you can share the deliciousness.

Melting Chocolate

Melting chocolate sounds so simple, but things can go wrong. If it gets too hot, it'll burn. If it doesn't get hot enough, it'll be lumpy. If it gets wet, it'll turn gritty and sludgy. For our peanut-butter swirl brownies, we use both unsweetened and semisweet chocolate, and we melt them together with the butter, which means there is less chance the chocolate will overheat and seize.

By placing the chocolates and butter in a heatproof bowl set over a pan holding a few inches of simmering water, you are creating a double boiler. A double boiler is a more gentle way of heating the ingredients, and helps to avoid scorching the chocolate.

The Best Way to Cut Brownies

  1. Don't rush the process: Wait until the brownies have cooled completely before cutting them into bars. You can speed up the process and maximize the fudgy texture of the treats by cooling them slightly, and then transferring the pan to the fridge for an hour. (Some bakers prefer to place the slightly cooled brownies in the freezer for a shorter time.)
  2. Once the peanut-butter swirl brownies are cooled, place a lightweight cutting board over the top of the pan. Flip it and set it on the counter. Gently pull the pan from the brownies to release them, then peel off and remove the parchment paper. Place another lightweight cutting board on top of the brownies and flip them right-side-up. (The bottom of the brownies will be on the cutting board.) 
  3. Use a sharp chef's knife to slice the brownies. This large knife will help you make clean cuts straight across the pan. Do not saw or move the knife back and forward as this may cause cracking in the brownies. Wipe it clean between each cut.

If you want perfect squares, do what food stylists do: Use a (clean) ruler. With the ruler as a guide, lightly score the brownies using the tip of a paring knife. Then cut following the guides you marked.

Directions

Ingredients for peanut butter swirl brownies
Credit:

Rachel Marek

  1. Preheat oven and prep pan; melt butter and chocolate:

    Preheat oven to 325°F. Line a buttered 8-inch square baking pan with foil or parchment paper, allowing 2 inches to hang over sides. Butter lining (excluding overhang); set pan aside. Put butter and chocolates in a heatproof medium bowl set over a pan of simmering water; stir until melted. Let cool slightly.

    Melted chocolate and butter
    Credit:

    Rachel Marek

  2. Whisk together dry ingredients:

    Whisk together flour, baking powder, and salt in a separate bowl, and set aside.

    Flour and whisk in bowl
    Credit:

    Rachel Marek

  3. Add sugar to chocolate mixture:

    Whisk granulated sugar into chocolate mixture.

    Sugar in bowl of melted chocolate with whisk
    Credit:

    Rachel Marek

  4. Add eggs, then vanilla:

    Add eggs, and whisk until mixture is smooth. Stir in vanilla.

    Eggs and vanilla in melted chocolate in bowl with whisk
    Credit:

    Rachel Marek

  5. Add dry ingredients:

    Add flour mixture; stir until well incorporated.

    Flour and melted chocolate in bowl with whisk
    Credit:

    Rachel Marek

  6. Make swirl filling:

    Stir together butter, confectioners' sugar, peanut butter, salt, and vanilla in a bowl until smooth.

    Peanut butter filling in bowl
    Credit:

    Rachel Marek

  7. Assemble:

    Pour one-third of batter into prepared pan, and spread evenly with a rubber spatula.

    Brownie batter and peanut butter in pan, bowls
    Credit:

    Rachel Marek

  8. Add dollops of swirl filling:

    Place dollops of filling (about 1 tablespoon each) about 1 inch apart on top of batter.

    Penut butter and brownie batter in pan
    Credit:

    Rachel Marek

    To swirl brownies, work quickly so that batter and filling don't set. Use two large spoons to drop dollops of filling on the first layer of batter about 1 inch apart. Repeat with next layer of batter and remaining filling.

  9. Add remaining batter:

    Drizzle remaining batter on top, and gently spread to fill pan.

    Brownie batter in pan with peanut butter
    Credit:

    Rachel Marek

  10. Add remaining filling:

    Place dollops of remaining filling on top.

    Peanut butter and brownie mix
    Credit:

    Rachel Marek

  11. Swirl filling into batter:

    With a butter knife, gently swirl filling into batter, running knife lengthwise and crosswise through layers, with the tip touching the bottom of the pan.

    Peanut butter swirl brownie mix
    Credit:

    Rachel Marek

  12. Bake:

    Bake until a cake tester inserted into brownies (avoid center and edges) comes out with a few crumbs but is not wet, about 45 minutes. Let cool slightly in pan, about 15 minutes.

    Peanut butter swirl brownies
    Credit:

    Rachel Marek

  13. Cool completely before cutting:

    Lift out brownies; let cool completely on a wire rack before cutting into squares.

    Peanut butter swirl brownies cooling on wire rack
    Credit:

    Rachel Marek

Storing

Leftover brownies are rarely a problem, but if you do have brownies to store, store them in an airtight container at room temperature or in the refrigerator. For optimal freshness, wrap each brownie individually in plastic wrap. 

Freezing

Brownies freeze well. Wrap them tightly in plastic wrap, then place in a freezer bag and store in the freezer for up to three months.

Frequently Asked Questions

  • What kind of peanut butter should I use for brownies?

    Use a smooth peanut butter; this is not a recipe where you want bits of peanut. Do not use natural peanut butter or homemade as they will have more oil and that may mean the swirl will not set up properly.

  • How do you know when brownies are done?

    Remember that the baking time in a recipe is a guideline; your brownies may take more or less time depending on various factors like your oven and the pan you used. The brownies are done when the top looks set. Test them using a toothpick: If there is wet batter on the toothpick, they need more time. If there are a few moist crumbs on the toothpick, they are done. (If the toothpick is clean, the brownies are over-baked.)

Other Brownie Recipes to Try:

Updated by
Victoria Spencer
Victoria Spencer, senior food editor, decorvow.com
Victoria Spencer is an experienced food editor, writer, and recipe developer. She manages the decorvow recipe archive and is always curious about new ingredients and the best techniques. She has been working in food media for over 20 years.

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