Some desserts feel like they were designed for celebrations, and these marshmallow frosted chocolate brownies are exactly that kind of sweet. I first made them for a summer block party when I wanted something with layers of texture: dense, fudgy brownies, a blanket of gooey marshmallows, and a shiny chocolate frosting that sets into a soft, sliceable cap. The first bite sparked a chorus of happy sighs, and they vanished faster than I could plate them.

What makes these special is the way each layer supports the next. The base is a deeply chocolatey brownie with big pockets of melted chocolate chunks, the middle is gently toasted marshmallow that turns stretchy and soft, and the top is a quick cocoa frosting that flows like a warm glaze and sets into a rich, velvety finish. I love how the sugar emulsified into warm butter gives the brownies that signature crackly top, while Dutch-process cocoa adds a sophisticated, dark-cocoa flavor. This is the pan I bring when I want guaranteed smiles and an empty tray to bring home.

Ingredients

• Unsalted butter: Use a quality, high-fat butter for the richest base and a glossy top. Melt gently to keep the batter smooth and avoid greasy edges.
• Granulated sugar: Whisked into warm butter, it emulsifies and builds that shiny, crackly top. A fine-grain brand dissolves more evenly.
• Canola oil: A touch of oil boosts moisture and keeps the brownies soft for days without making them cakey.
• Vanilla extract: Rounds out cocoa’s bitterness and deepens the chocolate notes; pure vanilla is worth the investment here.
• Large eggs: Added one at a time, eggs create structure and fudginess. Room-temperature eggs incorporate more smoothly.
• All-purpose flour: Just enough to bind without turning the brownies cakey. Measure lightly and level for accuracy.
• Dutch-process cocoa powder: Provides a dark, smooth chocolate flavor and a deep color. Choose a consistent brand for reliable results.
• Salt: A pinch sharpens the chocolate and balances sweetness; don’t skip it.
• Chocolate chunks: Roughly chopped dark or milk chocolate creates melty pockets. Bars melt better than chips due to lower stabilizers.
• Mini marshmallows: They soften and fuse into a gooey layer that pairs perfectly with the frosting.
• Salted butter (frosting): Adds instant flavor to the frosting and balances the sweetness without extra salt.
• Powdered sugar, cocoa powder, milk, and vanilla: Whisk into a pourable, glossy frosting that sets quickly and slices cleanly.

Instructions

Prep the pan and oven: Preheat the oven to 350°F. Line a metal 9x13-inch pan with parchment, leaving overhang on two sides for easy lifting. Lightly mist with nonstick spray so the parchment clings and the edges don’t stick. Using a metal pan ensures even heat and a shiny top. Emulsify butter and sugar: Melt the butter in a heavy saucepan over low heat. Off heat, whisk in the sugar until the mixture looks glossy and combined, with no separated butter. Stir for 1 to 2 minutes to help dissolve sugar crystals; this step promotes that classic crackly brownie surface. Add oil, vanilla, and eggs: Stir in the canola oil and vanilla until fully incorporated. Add eggs one at a time, whisking thoroughly after each until the batter looks smooth and slightly thick. Properly emulsified batter prevents greasy edges and helps the brownies stay fudgy. Fold in dry ingredients: Sift the flour, Dutch-process cocoa, and salt directly over the saucepan. Using a rubber spatula, fold just until no dry streaks remain. Overmixing develops gluten and can make brownies tough, so stop as soon as the batter is uniform. Add chunks and bake: Fold in most of the chopped chocolate, reserving a small handful for the top. Spread the batter evenly in the pan, sprinkle remaining chunks, and bake for about 25 minutes. The center should be set at the edges and slightly soft in the middle with a few moist crumbs. Add marshmallows: Remove the pan and quickly scatter mini marshmallows in an even layer. Return to the oven for 3 minutes until the marshmallows puff and just begin to melt. Do not overbake or they will dry out and brown too much. Cook the frosting: While the marshmallows rest, melt the salted butter in a saucepan over medium heat. Whisk in powdered sugar and cocoa, then add milk and vanilla to form a smooth, pourable frosting. It should be glossy and fluid but not thin; adjust with a teaspoon of milk if needed. Finish and set: Immediately pour the warm frosting over the marshmallow layer, nudging to the edges with a spatula. Let the pan cool until the frosting is set and matte, then lift out by the parchment. For the cleanest cuts, use a plastic knife or a sprayed metal knife wiped between slices.

Storage Tips

Let the frosting set fully before covering the pan. At room temperature, keep the brownies loosely covered for up to 2 days to maintain a soft marshmallow layer. For longer storage, refrigerate in an airtight container for up to 5 days; the chill firms the frosting and makes clean slices. To freeze, place cut squares on a sheet pan to firm, then wrap individually and store in a freezer-safe bag for up to 3 months. Thaw at room temperature, unwrapped, so moisture can escape and the tops stay glossy. If serving chilled, let brownies stand 10 to 15 minutes for the best texture.

Ingredient Substitutions

No canola oil? Swap vegetable oil one-for-one. Want a darker chocolate profile? Use all dark chocolate chunks and bump cocoa by 1 tablespoon while reducing flour by 1 tablespoon to keep balance. If you only have natural cocoa, you can use it in the frosting without issue; for the brownie base, stick to Dutch-process for richness and color. Replace unsalted butter in the batter with salted butter and reduce added salt slightly. If you prefer less sweetness, use bittersweet chocolate and a light hand when sprinkling extra chunks on top before baking. For a nutty twist, fold in 1 cup toasted chopped pecans or walnuts along with the chocolate chunks.

Serving Suggestions

These brownies are a showstopper on their own, but presentation ups the wow factor. Slice into neat squares and arrange on a platter lined with parchment for easy lifting. Add a light dusting of cocoa or a sprinkle of flaky salt to highlight the chocolate. Serve slightly warm with a scoop of vanilla ice cream, or chill the pan and serve with fresh berries to balance the richness. For gatherings, cut smaller two-bite pieces and stack them in tiers on a cake stand. A drizzle of warmed chocolate sauce over plated servings makes them feel restaurant-ready.

Cultural Background

Brownies are a quintessential American bake, beloved for their fudgy texture and simple prep. Versions topped with marshmallows and frosting evoke the spirit of potluck desserts and church cookbooks from the mid-20th century, when pantry-friendly toppings transformed everyday bars into party treats. The marshmallow layer nods to campfire nostalgia, while the glossy cocoa frosting channels the classic Texas sheet cake finish. These layers create a dessert that is both familiar and festive, perfect for holidays, bake sales, and weeknight celebrations alike.

Seasonal Adaptations

In summer, fold in 1 cup chopped dark chocolate and finish with a sprinkle of crushed freeze-dried berries over the frosting for a tangy pop. In fall, add 1 teaspoon espresso powder to the batter and a pinch of cinnamon to the frosting for warmth. Winter calls for peppermint: swap vanilla in the frosting for peppermint extract and sprinkle crushed candy canes on top. For spring, top with pastel sprinkles and serve chilled with fresh strawberries. Each variation keeps the base method the same while giving the brownies a seasonal personality.

Meal Prep Tips

For events, bake the brownies the day before and let the frosting set fully. Lift the slab from the pan, cover, and refrigerate. Slice cold for perfectly neat edges, then bring to room temperature before serving if you prefer a softer marshmallow. If you need to travel, keep the brownies in the original pan, cover tightly, and transport with a cold pack in warm weather. To portion for lunch boxes, cut smaller squares and store in single layers separated by parchment so the frosting stays pristine.

When you need a dessert that thrills without fuss, these brownies deliver every time. From the fudgy base to the nostalgic marshmallow layer and shiny frosting, each bite feels like a celebration. Make them once, and they will become your go-to when you want guaranteed smiles.