Peanut Butter Swirl Brookies (pb Cup Inspired)

Gooey brownie meets chewy cookie with rich peanut butter ribbons—party-worthy bars you can whip up fast, no mixer needed.

If you’ve ever wished a brownie and a cookie would stop flirting and just get married, you’re in the right kitchen. These mashup bars stack fudgy brownie richness, chewy chocolate-chip cookie comfort, and a bold peanut butter swirl that tastes like a leveled-up candy cup. The payoff is ridiculous: glossy top, soft middle, and ribbons of salty-sweet PB in every bite. No stand mixer. No drama. Just smart steps, everyday ingredients, and a pan of crowd-pleasers you’ll want on repeat.

The Secret Behind This Recipe

The magic isn’t luck; it’s structure and contrast. We use a fudgy brownie base with just enough flour to set while staying plush, then dot it with a soft cookie dough that bakes into chewy pockets. The PB swirl isn’t just straight peanut butter—adding a touch of powdered sugar and oil makes it silky enough to ribbon and prevents dry, baked PB streaks.

Layering matters. Spread the brownie batter, scatter spoonfuls of cookie dough, then dollop and swirl the peanut butter. Swirl in figure-eights so you get thick ribbons, not chaotic marbling that disappears. Bake until the edges are set and the center still looks slightly soft. Trust the carryover heat; you’re aiming for moist crumbs on the toothpick, not a squeaky-clean skewer.

Ingredients

Brownie Layer

• 1/2 cup (113 g) unsalted butter, melted
• 1 cup (200 g) granulated sugar
• 1/3 cup (80 ml) neutral oil (vegetable or canola)
• 2 large eggs, room temperature
• 1 teaspoon vanilla extract
• 1/2 cup (50 g) unsweetened cocoa powder (Dutch-process preferred)
• 1/2 teaspoon espresso powder (optional, for deeper chocolate flavor)
• 3/4 cup (95 g) all-purpose flour
• 1/4 teaspoon fine salt

Cookie Layer

• 1/2 cup (113 g) unsalted butter, softened
• 1/2 cup (100 g) packed light brown sugar
• 1/4 cup (50 g) granulated sugar
• 1 large egg
• 1 teaspoon vanilla extract
• 1 1/4 cups (155 g) all-purpose flour
• 1/2 teaspoon baking soda
• 1/4 teaspoon fine salt
• 3/4 cup (130 g) semisweet chocolate chips

Peanut Butter Swirl

• 1/2 cup (130 g) creamy peanut butter (regular, not “natural”)
• 2 tablespoons powdered sugar
• 1 tablespoon neutral oil (or melted butter), to loosen
• 1/4 teaspoon fine salt
• Optional: 2 tablespoons chopped roasted peanuts or mini PB cup pieces

Pan Prep

• 9×9-inch square pan, lined with parchment and lightly greased

Instructions

1. Preheat and prep: Heat the oven to 350°F (175°C). Line a 9×9-inch pan with parchment, leaving overhang. Lightly grease the sides.
2. Make the PB swirl: In a small bowl, stir peanut butter, powdered sugar, oil, and salt until smooth and pourable. You want a thick ribbon consistency—add a teaspoon more oil only if needed. Set aside.
3. Brownie batter: In a medium bowl, whisk together melted butter, sugar, and oil until glossy. Whisk in eggs and vanilla for 30–45 seconds until slightly thick. Whisk in cocoa, espresso powder, and salt. Switch to a spatula and fold in flour just until no dry streaks remain. Don’t overmix.
4. Cookie dough: In another bowl, beat softened butter with brown and granulated sugars until creamy (about 1 minute; a hand whisk works). Mix in egg and vanilla. In a separate bowl, stir flour, baking soda, and salt, then fold into the butter mixture. Fold in chocolate chips until evenly dispersed.
5. Assemble: Spread brownie batter into the pan in an even layer. Drop spoonfuls of cookie dough all over the surface (think small golf balls), pressing lightly so they nestle into the brownie.
6. Swirl time: Spoon the peanut butter mixture in generous dollops across the top. Use a butter knife or skewer to swirl in figure-eights, dragging through both batters. Aim for visible ribbons; resist the urge to over-swirl into uniformity.
7. Bake: Bake for 24–28 minutes, until the edges are set and the center looks slightly soft. A toothpick should come out with moist crumbs, not wet batter. If you’re using a 9×13-inch pan, start checking at 20–22 minutes; for 8×8-inch, add 3–5 minutes.
8. Finish: Cool in the pan on a rack for 30–45 minutes to let the bars set. Sprinkle flaky sea salt on top if you like that sweet-salty vibe. Lift out with parchment and slice into 16 squares. Serve slightly warm (ice cream strongly encouraged).

Storage Instructions

• Room temp: Store in an airtight container for up to 3 days. They stay soft thanks to the PB swirl.
• Fridge: Keep tightly sealed for 5–6 days. Warm briefly to re-soften.
• Freezer: Wrap bars individually, then stash in a freezer bag for up to 2 months. Thaw at room temp 30 minutes, or microwave 15–20 seconds.
• Reheat: For best texture, warm in a 300°F oven for 6–8 minutes. Microwave is fine in a pinch; don’t overdo or the PB can get dry.

Nutritional Perks

We’re not calling these “health bars,” but let’s count the wins. Peanut butter brings protein and satiating fats that keep one square from becoming six (ideally). Cocoa supplies polyphenols—aka antioxidant goodness—especially if you use Dutch-process and dark chips.

Choose semisweet or dark chocolate chips for a bit less sugar. Want a small upgrade? Swap 1/4 cup of flour in the cookie dough for fine almond flour to bump up healthy fats and fiber. Balance is the move here: decadent, sure, but not a sugar bomb you regret.

Pitfalls to Watch Out For

• Natural PB drama: Natural peanut butter can separate and bake up oily or dry. Use regular creamy PB for reliable swirls.
• Overbaking: If you wait for a clean toothpick, you’ll get dry edges and a tight crumb. Look for moist crumbs, not batter.
• Overmixing dough: Tough cookie pockets come from overworking flour. Fold just until combined.
• Over-swirl syndrome: Too much swirling blends everything into one brown layer. Keep ribbons bold and visible.
• Hot butter scramble: If your butter is scorching hot and you add eggs, you risk curdling. Let melted butter cool slightly before whisking.
• No parchment? Don’t skip the liner. Brookies like to stick, and wrestling a pan with a spatula is not a personality trait.
• Uneven thickness: Clumps of cookie dough too big can sink. Use small spoonfuls and spread them out.

Mix It Up

• PB Cup Crunch: Sprinkle chopped mini PB cups and roasted peanuts over the top before baking for extra texture.
• Sweet-salty flex: Finish with flaky sea salt right after baking. The contrast is elite, IMO.
• Pretzel party: Crush salted pretzels and fold into the cookie dough for crunch that won’t go soggy.
• PB&J swirl: Dollop raspberry or strawberry jam alongside the peanut butter and swirl together. Dessert nostalgia unlocked.
• Brown butter upgrade: Brown the cookie dough butter for nutty depth. Cool to room temp before mixing.
• Gluten-free swap: Use a quality 1:1 GF flour in both layers. Expect 2–3 extra minutes bake time.
• Vegan option: Use coconut oil in the brownie, vegan butter in the cookie, and flax egg (1 tbsp flax + 3 tbsp water) for each egg. Pick dairy-free chips.
• Espresso hint: Keep the espresso powder for a darker chocolate tone. Coffee lovers will notice in the best way.

FAQ

Can I use natural peanut butter for the swirl?

You can, but it’s a gamble. Natural PB separates and can bake up greasy or dry. For consistent ribbons, use regular creamy peanut butter and loosen it with a bit of oil and powdered sugar. FYI, the small tweak makes a big difference.

What pan size works best?

A 9×9-inch pan gives thick, bakery-style squares. You can use a 9×13-inch for thinner bars (start checking doneness 20–22 minutes) or an 8×8-inch for extra thickness (add 3–5 minutes). Adjust baking time based on visual cues—set edges, soft center.

How do I know when the brookies are done?

Look for set edges, a slightly soft center, and a toothpick that comes out with moist crumbs. If it’s wet batter, give it more time. If it’s squeaky clean, you overshot. Pull them at the sweet spot so carryover heat finishes the set.

Do I need a mixer?

Nope. A whisk and a spatula are perfect. Mix the brownie batter by hand, and cream the cookie dough with a whisk or wooden spoon. Less gear, less cleanup, same great texture—your future self says thanks.

Can I make these ahead and freeze?

Yes. Cool completely, slice, wrap each square, and freeze for up to 2 months. Thaw at room temperature or warm in a 300°F oven for 6–8 minutes. The PB swirl actually keeps thawed bars moist.

Why did my cookie dough sink into the brownie?

Usually the dollops were too big or the brownie batter was too thin. Use small spoonfuls and press them lightly into the surface. If your brownie batter looks runny, add an extra tablespoon of flour. Balance is the goal.

Can I double the recipe?

Absolutely. Double everything and bake in a 9×13-inch pan for thicker bars, or a half-sheet pan for more squares with less depth. Monitor visual cues and start checking doneness early; ovens don’t all play by the same rules, IMO.

How do I get clean slices?

Let the bars cool at least 30–45 minutes. Lift out with parchment, use a long sharp knife, and wipe the blade between cuts. A small chill (15 minutes in the fridge) helps if you’re going for perfect edges.

The Bottom Line

These bars deliver the best of three worlds: fudgy brownie base, chewy cookie pockets, and thick PB ribbons that taste like your favorite candy but bake easier. The process is simple, the ingredients are basic, and the payoff is high. Want a bake-sale win, a game-night finisher, or a weeknight flex? This pan checks every box—and yes, you’ll want seconds.