Small Batch BIG Chocolate & Peanut Butter Lava Rock Cookies (Voted Best of the Year)
After many test runs developing this recipe, I think we finally nailed this small batch BIG cookie! But, we’ll let you decide.
Thick, gooey, and irresistibly rich, these NYC- or Crumbl-style Small Batch BIG Chocolate & Peanut Butter Lava Rock Cookies feature a molten peanut butter center surrounded by golden dough packed with semi-sweet chocolate and roasted peanuts. —Stone
As satisfying to break open as they are to eat, they’re sure to impress not only here on screen but also on your table enjoyed by family and friends.
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The Journey to the Perfect Small Batch BIG Chocolate & Peanut Butter Lava Rock Cookie — Oh the Drama of it All!
At Mountaintop Kitchen, some recipes are born golden on the first try. This wasn’t one of them. We are first and foremost a test kitchen, where we develop trial recipes: some purely from imagination of what could be and others inspired by something we tasted somewhere or saw someplace and wanted to incorporate our own twist in conjuring up something unique and scrumptious. I was recently vacationing in the Grand Canyon and around northern Arizona and came upon a muffin that mixed chocolate and peanuts together. A few days later in Flagstaff, I happened upon a candy store named Sweet Shoppe, where the confectioner asked me if I’d like to try their Chocolate Peanut Butter Fudge. It was creamy and oh so delicious. I felt like the universe was pointing me in a sweetly determined direction: the quintessential pairing of chocolate and peanuts. As I walked through the quaint downtown Flagstaff streets and plazas, I had an epiphany: “I will cookie-ify these flavors with a gooey surprise inside.” So that’s what I set out to accomplish.
The Small Batch BIG Chocolate & Peanut Butter Lava Rock Cookie—my take on the iconic crumbl or NYC-style cookie (more crumbl that NYC) and my newly acquired Arizona musings—took five batches, multiple late-night test bakes, and more peanut butter than I’d like to admit to get it just right. And while my test kitchen may have looked like a chocolate and peanut butter war zone by the end, the journey was worth it.
Batch 1: The Collapse
I started with the dream: a gooey peanut butter center inside a thick, bakery-style cookie that oozes when you break it in half. I whipped up a basic cookie dough and plopped a scoop of peanut butter in the middle.
The result? A flat, greasy mess. The peanut butter leaked everywhere, and the cookie spread into a thin pancake with barely any structure. Not even good enough for crumbs over ice cream.
Lesson learned: Peanut butter lava needs a barrier and a freeze.
Batch 2: The Brick
For my second try, I froze the peanut butter into balls and encased them in a sturdier dough. But I overcorrected. I reduced the sugar, added too much flour, and ended up with a dry, bready cookie that no one wanted to finish. The peanut butter stayed in, but the texture was all wrong—more biscuit than cookie. This is what test kitchens do to perfect recipes.
Lesson learned: NYC-style cookies need bold richness. Don’t shy away from fat or sugar.
Batch 3: The Spread
I found a sweet spot with softened butter and a better flour-to-fat ratio. The dough came together beautifully, but I didn’t chill the cookies long enough, and they spread again. This time they tasted amazing—but the dramatic pull-apart lava moment I was chasing? Nowhere to be seen.
Lesson learned: Chill time is crucial for structure. A cold cookie is a bold cookie.
Batch 4: Getting Closer
I chilled the assembled cookies overnight, and for the first time, everything came together—the crispy edge, the gooey center, the peanuts toasted on the outside. The only flaw? The peanut butter filling was a little too stiff. Not quite lava. More like “peanut clay.” Visuals are just as important as taste to serious bakers on the move.
Lesson learned: Add a touch of butter and sugar to the filling to soften the flow.
Batch 5: The Lava Rock Is Born
By the fifth test, I’d dialed in every ratio. The dough had cold (not room temperature) cubed butter for texture, brown and white sugars for chew and crisp, chocolate shards for drama, and just enough chopped peanuts for crunch. The peanut butter center—softened with a little powdered sugar and butter—melted just right in the oven. Finally, when I cracked one open, the nutty lava flowed.
Golden. Thick. Gooey. Crunchy. Perfect.
I knew it the moment I pulled that cookie apart at put it into my mouth: This is the one.
What You’ll Taste
This isn’t just another peanut butter cookie. It’s an experience: the snap of roasted peanuts on the outside, the fudgy chocolate swirled throughout, and that rich, creamy peanut butter core that oozes out like molten gold.
It’s over the top in all the right ways. And it’s made to be shared—with a friend or with the internet (That’s you!).
Bake it. Break it. Eat it.
The Recipe:
On Measuring Ingredients: My preferred method of measuring is weight by grams. Baking by volume rather than weight can lead to varied and unexpected results. Flour is especially problematic when measured by volume (sifted, not sifted, spooned, not spooned, fluffed or not … you get the point). Grams are always the same; they are your friend as a baker. King Arthur Baking Company’s Ingredients Weight Chart is helpful for converting recipe weights.
On Altitude Adjustments: Before measuring ingredients, preheating your oven, or setting your timer; it’s important to consider any necessary adjustments for baking at higher altitudes, which is generally considered to be 3,500ft and above. Most recipes are written for sea level up to 3,500ft. Take at look at our baking at High-Altitude Baking Adjustments page for guidance.
Yield: 6 large cookie
Serving Size: 1 cookie
Prep Time: 25 minutes
Chill Time: 1 hour (minimum)
Bake Time: 18 to 20 minutes
Cool Time: 10 minutes
Total Time: 1 hour 45 minutesNote: This cookie recipe, as with many, will work at elevations at up to 7,200 feet. It has not been tested at altitudes higher than this. However, cookie recipes are much hardier and tolerant of altitude variations than cakes and other more delicate bakes.
For the peanut butter filling (6 balls):
6 tablespoons creamy peanut butter (100g)
2 tablespoons confectioners’ sugar (20g)
1 tablespoon unsalted butter, softened (14g)
⅛ teaspoon pinch of salt
For the cookie dough (6 cookies):
13 tablespoons unsalted butter, cold and cubed (180g)
⅔ cup, packed light brown sugar (130g)
⅓ cup granulated sugar (70g)
1 large egg (50-55g w/shell)
1 teaspoon vanilla extract
2 cups all-purpose flour (240g)
1 teaspoon baking powder
½ teaspoon baking soda
½ teaspoon kosher salt
¾ cup semi-sweet chocolate, chopped into chunky pieces (130g)
½ cup roasted salted peanuts, coarsely chopped — divided (80g)
Thanks for stopping by our little place, the Mountaintop Kitchen, for home bakers everywhere!
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Stone—The Mountaintop Baker👨🏼🍳
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