Sheet Pan Brownies using Box Mix

Indulge in the ultimate combination of convenience and decadence with this recipe for Sheet Pan Brownies using Box Mix.

Made with a simple boxed brownie mix and chopped pecans, the baked brownies are topped with mini marshmallows that are then baked till lightly melted.

Then to make these brownie mud bars even better, a homemade chocolate sauce is drizzled on top right before serving.

Check out all the other easy desserts that you how easy it can be to create a sweet treat that everyone will enjoy!

Indulge in the ultimate sweet treat of fudgy brownies, crunchy pecans, gooey marshmallows, and rich chocolate sauce!

Drizzled with a homemade chocolate sauce that's rich, creamy, and perfectly sweetened, every bite is the perfect combination of flavors and textures.

Easy to make and even easier to devour, these semi-homemade brownies are sure to become a family favorite for any occasion.

Looking for more boxed brownie or cake mix recipes? Try my Brownie Mix Mint Chip Cookies , German Chocolate Cake recipe  or my Peanut Butter Brownies...yum!

Easy Brownie Baking Tips

Prep the Pan: Grease the sheet pan generously with non-stick cooking spray, and consider lining it with parchment paper for easier removal of the brownies.

Choose the Right Size Pan: Use a sheet pan that's the appropriate size for the amount of brownie batter you have. For a standard box mix, a half-sheet pan (about 13x18 inches) works well.

Follow the Instructions: While using a box mix simplifies the process, it's important to follow the instructions listed below and on the recipe card carefully. Pay attention to measurements for ingredients, mixing times, and baking temperatures.

Avoid Overmixing: Be careful not to overmix the batter, as this can result in tough or dense brownies. Mix just until all the ingredients are incorporated.

Check for Doneness: Since sheet pan brownies are thinner than traditional brownies, they may bake more quickly. Start checking for doneness a few minutes before the recommended baking time to avoid overbaking. A toothpick inserted into the center should come out with a few moist crumbs clinging to it.

Cool Completely: Allow the brownies to cool completely in the pan before slicing and serving. This helps them set and makes for cleaner slices.

🛒Helpful Kitchen Tools

Ingredients

This is an overview of the ingredients and instructions. Be sure to see the recipe card below for exact quantities, detailed instructions and special notes.

Step-by-Step Instructions

Step 1: In a mixing bowl, prepare the brownie mix according to the instructions on the box.

Step 2: Then gently fold in the chopped pecans until evenly distributed.

Baking Instructions

Step 3: Spread the brownie batter onto the prepared baking sheet, ensuring an even layer.

Step 4: Bake in a preheated 350°F oven for approximately 15 minutes, or until a toothpick inserted into the center comes out clean.

Add the Mini Marshmallows

Step 5: Remove the brownies from the oven and evenly distribute the mini marshmallows over the top.

Step 6: Return the pan to the oven for an additional 3-5 minutes, or until the marshmallows have puffed up and become and slightly golden. Allow to cool while you prepare the homemade chocolate sauce.

Homemade Chocolate Sauce

Step 7: Melt the butter, milk, salt, and unsweetened cocoa powder together in a saucepan over medium heat.

Step 8: Stir continuously until fully melted and combined, then remove from heat and mix in vanilla and powdered sugar until smooth; if too thick, add more milk to adjust consistency.

Step 9: Once the brownies have cooled, drizzle the chocolate sauce diagonally over the top, covering them evenly.

Step 10: Finally, cut the brownies into bars, serve.

Storing and Thawing Tips

Room Temperature: Allow the brownies to cool completely at room temperature first. Once cooled, cut them into individual bars and transfer them to an airtight container or a tightly sealed storage bag.

Layer parchment paper between the bars to prevent sticking. Store the brownies at room temperature for up to 3 days for optimal freshness and texture.

Freezer: Wrap leftover brownies tightly in plastic wrap and aluminum foil before freezing. Thaw frozen brownies in the refrigerator overnight before serving or enjoy them straight from the freezer for a chilled treat.

Thawing Tips: Thaw frozen brownies in the refrigerator overnight before serving or enjoy them straight from the freezer for a chilled treat.

Reheating Tips: You can also enjoy them warmed up in the microwave by placing a single brownie on a microwave-safe plate and heat on high for 15-20 seconds, or until warmed to your liking.

Top Recipe Tips

• Watch the marshmallows closely while they're in the oven. Marshmallows can quickly go from golden and gooey to burnt if left unattended.
• Keep a close eye on them during the last few minutes of baking, and be ready to remove the brownies from the oven as soon as the marshmallows are lightly toasted and puffed.
• This ensures that they're perfectly melted and adds a delightful texture without becoming overly charred.

Try these recipes next...

Like the idea of baking desserts in a sheet pan? Try my Sheet Pan Chocolate Chip Cookies! Or this fun recipe for Brownies in a Mason Jar Recipe.

Or you might enjoy this recipe for Cherry Berry on a Cloud that's a layer of meringue, cherries, sweetened whipped cream, marshmallow, and cream cheese.

📖 Recipe Card

Lois

Sheet Pan Brownies with Box Mix

5 from 1 vote

Made with pantry ingredients, these sheet pan brownies using box mix with pecans are topped with marshmallows and a homemade chocolate sauce.

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Prep Time 20 minutes mins

Cook Time 15 minutes mins

Total Time 35 minutes mins

Servings: 24

Course: Desserts

Cuisine: American

Calories: 212

Ingredients Method Nutrition Video Notes

Ingredients

  

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For the Brownies

• 16.3 ounce Brownie mix box + ingredients listed on the back of the box
• 1 cup pecans chopped
• 10 ounce mini marshmallows

For the Homemade Chocolate Sauce

• ⅓ cup unsweetened cocoa powder
• ¼ cup milk
• ¼ cup unsalted butter
• ¼ teaspoon salt
• 2 cups powdered sugar
• 1 teaspoon vanilla extract

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Method

 

1. Preheat the oven to 350°F and line a baking sheet with parchment paper for easy cleanup.
2. In a mixing bowl, prepare the brownie mix according to the instructions on the box, then gently fold in the chopped pecans.
3. Spread the brownie batter onto the prepared baking sheet, ensuring an even layer, and bake in the preheated oven for approximately 15 minutes, or until a toothpick inserted into the center comes out clean. Keep in mind that the bake time may be shorter than indicated on the box due to the thinner layer of batter.
4. Once baked, promptly remove the brownies from the oven and evenly distribute the mini marshmallows over the top. Return the pan to the oven for an additional 3-5 minutes, or until the marshmallows have puffed up and become soft and slightly golden.
5. Allow the brownies to cool in the pan before proceeding.
6. While the brownies are cooling, prepare the chocolate sauce by melting the butter, milk, salt, and unsweetened cocoa powder together in a saucepan over medium heat. Stir continuously until fully melted and combined, ensuring there are no lumps.
7. Remove the saucepan from the heat and stir in the vanilla and powdered sugar until smooth and creamy. If the sauce is too thick for drizzling, simply add a splash more milk to achieve the desired consistency.
8. Once the brownies have cooled, drizzle the chocolate sauce diagonally over the top, covering them evenly.
9. Finally, cut the brownies into bars, serve, and enjoy the delicious combination of fudgy brownies, crunchy pecans, gooey marshmallows, and rich chocolate sauce!

Nutrition

Serving: 1ServingCalories: 212kcalCarbohydrates: 36gProtein: 2gFat: 7gSaturated Fat: 2gPolyunsaturated Fat: 1gMonounsaturated Fat: 3gTrans Fat: 0.1gCholesterol: 5mgSodium: 92mgPotassium: 40mgFiber: 1gSugar: 26gVitamin A: 66IUVitamin C: 0.05mgCalcium: 9mgIron: 1mg

Notes

• Use a spatula to spread the brownie batter evenly in the sheet pan, ensuring that it reaches all corners and edges for uniform baking.
• Keep in mind that the baking time may be shorter than indicated on the back of the box due to the thinner layer of batter.

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