The marshmallows puff up in the oven and turn the top of each brownie soft and cloudlike, while the edges underneath stay dark and chewy. I like that contrast: a little like hot chocolate with something sweet melting into it, but easy to cut into squares. These hot chocolate brownies get their chocolate flavor from both semisweet chocolate and cocoa, so the center tastes rich without relying on a thick frosting.
The batter comes together in one bowl, and the topping goes on near the end rather than baking into the brownies from the start. That keeps the marshmallows visible and pillowy instead of disappearing into the chocolate. Once the pan has cooled, the parchment overhang makes it simple to lift out the whole slab for cutting. The finished squares have a fudgy middle, a tender top, and little peaks of marshmallow.
Kitchen Note
Coat the parchment with cooking spray, not just the pan. The marshmallows can cling to an ungreased liner, and that little bit of spray makes the parchment much easier to lift away cleanly.
Save these hot chocolate brownies for a bake when you want fudgy chocolate squares topped with soft, puffed marshmallows.
Why Hot Cocoa Mix and Cocoa Powder Aren’t Interchangeable
Sweetened hot cocoa mix and unsweetened cocoa powder might look like two versions of the same ingredient, but they do different jobs here. The mix brings sweetness along with a familiar hot-chocolate taste. The unsweetened cocoa adds a more concentrated chocolate note without adding more sugar. Semisweet chocolate rounds that out with a smooth, deep base.
Replacing the hot cocoa mix with the same amount of plain cocoa powder would throw off the balance: you’d lose the sugar and the particular sweetness that makes these brownies taste like hot chocolate. Adding extra cocoa in its place wouldn’t fix that; it would push the chocolate flavor sharper while leaving the batter less sweet. Keep both powders in the mix, and you get a brownie that tastes chocolatey first, with the sweet cocoa note coming through in the finish.
The Chocolate and Marshmallows That Shape Every Bite
- Semisweet chocolate — Finely chopped pieces melt evenly with the butter. A basic baking bar works well; there’s no need for an expensive chocolate here. Semisweet chocolate chips can stand in for the chopped chocolate in the same weight, though their stabilizers may make the melted mixture a little thicker.
- Unsalted butter — Butter gives the brownies their rich, tender crumb, and unsalted lets the kosher salt stay in balance. A store-brand butter is fine; I wouldn’t swap in oil, which changes the texture and how the chocolate mixture comes together.
- Sweetened hot cocoa mix and unsweetened cocoa — Choose a familiar sweetened mix rather than a sugar-free or strongly flavored version, which changes the sweetness and taste. The cocoa powder can be an everyday unsweetened brand; a specialty tin isn’t needed for a good chocolate base.
- Eggs — The eggs help bind the batter and give it structure as it bakes. Use large eggs as listed; there’s no useful substitute that keeps this brownie texture the same.
- All-purpose flour — Flour gives the center enough structure to hold together without making it cakey. Measure it without packing it down. For a gluten-free version, use a cup-for-cup gluten-free baking flour in place of the all-purpose flour.
- Mini marshmallows — Mini marshmallows spread into a soft topping without weighing down the brownie layer. The store-brand bag works just as well as a premium one, as long as the marshmallows are fresh and soft.
From Smooth Chocolate Batter to a Puffed Marshmallow Top
Set Up the Pan and Melt the Chocolate
Heat the oven to 350°F and line an 8-inch square metal baking pan with parchment, leaving enough overhang to lift the brownies later. Coat the parchment with nonstick cooking spray. In a heatproof bowl, microwave the butter and finely chopped semisweet chocolate in 20-second bursts, stirring after each one, until smooth; this usually takes about 1 to 1 1/2 minutes. If a few small pieces remain, stir before microwaving again so the chocolate doesn’t get hotter than it needs to.
Whisk Until the Batter Turns Glossy
Whisk the granulated sugar, sweetened hot cocoa mix, unsweetened cocoa powder, and kosher salt into the melted chocolate mixture. Add the eggs and vanilla, then whisk until the batter looks glossy and evenly combined. Scrape around the bowl as you whisk so no dry cocoa mix stays tucked along the sides. The batter should look smooth before the flour goes in.
Fold Gently and Bake to the Moist-Crumb Cue
Add the all-purpose flour and fold just until no dry streaks remain; stop there rather than beating the batter smooth. Spread it evenly into the prepared pan so the corners don’t bake thinner than the center. Bake for 22 to 26 minutes, until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs. A completely clean toothpick can mean the brownies have gone past the fudgy stage.
Puff the Marshmallows and Let the Slab Set
Scatter the mini marshmallows evenly over the brownies, then return the pan to the oven for 3 to 5 minutes, just until they’re puffed. Keep an eye on them; the goal is a soft, lifted topping, not a browned layer. Cool the brownies completely in the pan for at least 2 hours, then use the parchment overhang to lift them out. Cut into squares once the slab is cool, when the chocolate layer has had time to firm up.
Three Ways to Adapt These Hot Chocolate Brownies
Make Them Gluten-Free
Replace the all-purpose flour with the same amount of cup-for-cup gluten-free baking flour. The centers may be a little more delicate, so let the brownies cool completely before lifting and cutting them.
Use Semisweet Chocolate Chips
Swap the finely chopped semisweet chocolate for the same weight of semisweet chocolate chips. The chips may melt into a slightly thicker mixture, but they keep the brownies’ chocolate-forward flavor intact.
Leave Off the Marshmallows
Skip the topping for a straightforward chocolate brownie with a firmer surface and no extra sweetness on top. Bake the brownie layer as usual, then cool it in the pan before cutting.
Storage and Reheating
- Refrigerator: Store in an airtight container for up to 5 days. The marshmallow topping will firm up, and the brownies will become denser when chilled.
- Freezer: Freeze cut squares in a single layer until firm, then store them airtight with parchment between layers for up to 2 months. Thaw before serving.
- Reheating: These are best at room temperature. If you want a warm square, microwave it briefly in short bursts; long heating makes the marshmallow topping sticky and soft.
Questions That Come Up When Baking These Brownies
Hot Chocolate Brownies
Ingredients
Equipment
Method
- Heat the oven to 350°F.
- Line an 8-inch square metal baking pan with parchment paper, leaving an overhang, and coat the parchment with nonstick cooking spray.
- Microwave the butter and semisweet chocolate in a heatproof bowl in 20-second bursts, stirring each time, until melted and smooth, about 1 to 1 1/2 minutes.
- Whisk the granulated sugar, sweetened hot cocoa mix, unsweetened cocoa powder, and kosher salt into the chocolate mixture.
- Whisk in the eggs and vanilla extract until glossy.
- Fold in the all-purpose flour just until no dry streaks remain.
- Spread the batter evenly in the prepared pan.
- Bake for 22 to 26 minutes, until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs.
- Scatter the mini marshmallows evenly over the brownies.
- Bake for 3 to 5 minutes, until puffed.
- Cool completely in the pan, at least 2 hours.
- Lift the brownies out using the parchment and cut into squares.
