Peanut Butter Swirl Brownies

side view of the pan of baked brownies with a peanut butter swirl on top.

Peanut Butter Swirl Brownies with a fudgy brownie base and topped with swirls of sweetened creamy peanut butter. This peanut butter brownie recipe is so easy to make because it starts with a brownie box mix, and a simple 4 ingredient peanut butter swirl batter.

Course Dessert

Cuisine American

Keyword peanut butter swirl brownies

Prep Time 10

Cook Time 25

Cooling Time 30

Total Time 1 5

Servings

Calories 260kcal

Author Jessica - Together as Family

Equipment

Ingredients

1 box (18.3 oz) fudge brownie mix (plus the ingredients called for)
1 cup creamy peanut butter
2 tablespoons powdered sugar
½ teaspoon vanilla extract
⅛ teaspoon sea salt (just a small pinch)

Instructions

Preheat the oven to 350℉. Lightly spray a 9x13-inch baking dish or cake pan with nonstick cooking spray. You can also line the baking dish with parchment paper for easier removal.
Prepare the brownie mix according to directions on the back of the box, using the listed ingredients (eggs, vegetable oil, and water), in a large bowl. Stir all the ingredients together until they are thoroughly combined and no dry pockets remain in the batter, but don't overmix the brownie batter.
1 box (18.3 oz) fudge brownie mix
Place the peanut butter into a microwave-safe heatproof bowl and heat for 30-60 seconds just until it loosens up and becomes smooth and pourable. It should easily flow off a spoon in a thin ribbon.
1 cup creamy peanut butter
Once it reaches a good consistency, stir in the powdered sugar, vanilla extract, and salt. Mix until the batter thickens slightly but is still soft and easy to spoon.
^{*If it firms up too much while mixing, pop it back in the microwave for another 5-10 seconds to loosen it again.}
2 tablespoons powdered sugar, ½ teaspoon vanilla extract, ⅛ teaspoon sea salt
Pour the brownie batter into the prepared baking dish and smooth the top with a spatula. Use a spoon to drop dollops of the peanut butter batter all over the top of the brownie batter, or you can drizzle/pour the peanut butter mixture in a line/row pattern over top the brownie batter.
Use a butter knife or a skewer to gently swirl the peanut butter mixture into the brownie batter. Go for a pretty marbled effect/pattern without fully blending it into the brownie batter all the way.
Bake for 25-35 minutes or until a toothpick inserted into the center comes out with only a few moist crumbs and not wet batter.
Let the brownies cool completely in the pan on a cooling rack.
Once the brownies have cooled, cut into squares and enjoy!
^{*You can eat the brownies completely cooled to room temperature (about 30-45 minutes cooling time) OR eat them slightly warmed (20 minute cooling time) so that way they will still cut nicely.}

Notes

Start checking for doneness around the 20 to 25-minute mark. When you insert a toothpick or cake tester into the center, you should see a few moist crumbs clinging to it. You don't want to see wet batter on the toothpick as that means the brownies need more time to bake through. You also don't want to overbake the brownies or else they will be dry.
I recommend lining the pan with parchment paper. Parchment paper (just like for cookies) helps the brownies bake more evenly and it helps the bottom of the brownies from over browning. I spray the pan first with parchment paper and then press my parchment paper into the pan; the spray helps it adhere and stick better to the pan, so it's easier to spread the brownie mixture into it.
The brownies can be eaten slightly warmed or at room temperature. If eating warm and gooey, I still recommend letting the brownies cool for at least 30 minutes, that way, they will cut nicely and not fall apart; but still be warm and soft and gooey for serving.
Do not use any peanut butter labeled as 'all-natural' or any that has a thick oil layer on top that must be stirred before using. Creamy peanut butter will give you a nice smooth peanut butter swirl, while all-natural peanut butter tends to crack and bake up more dry and dense.
The peanut butter mixture should be pourable and smooth enough that you can pour it in a line/row pattern (as shown in the process pics in the post).

Nutrition