1. Preheat the Oven:

   • Preheat your oven to 325°F (165°C).

   • Line a 9×13-inch glass baking dish with parchment paper, leaving an overhang for easy removal, or grease well.

2. Prepare the Brownie Batter:

   • Prepare 1 box brownie mix according to package instructions (typically mixing with eggs, oil, and water).

   • Stir until smooth and set aside.

3. Layer the Graham Crackers:

   • Lay 7–9 graham crackers in a single layer across the bottom of the prepared baking dish, covering as much surface as possible. Break crackers to fit if needed.

4. Add the First Brownie Layer:

   • Using a spatula, spread a thin layer of brownie batter over the graham crackers, covering them as evenly as possible. Use about half the batter, reserving the rest for the top layer.

5. Add the Oreo Layer:

   • Arrange 8 oz Mini Oreos in a single layer over the brownie batter, pressing lightly to adhere. If using full-sized Oreos, use about 15–18 and space evenly.

6. Add the Marshmallow Layer:

   • Cut 20 Jet-Puffed S’moreMallows in half to create thinner pieces (or use whole if thinner marshmallows are preferred).

   • Layer the halved marshmallows (about 40 halves) over the Oreos, covering as much surface as possible.

7. Top with Remaining Brownie Batter:

   • Spread the remaining brownie batter over the marshmallows and around the sides of the Oreos, using a spatula to smooth it as evenly as possible. Ensure the marshmallows are mostly covered.

8. Bake:

   • Bake in the preheated oven for 35–45 minutes, checking at 35 minutes. The brownies are done when a toothpick inserted in the center comes out with a few moist crumbs (slight overbaking is preferred for structure).

   • Adjust baking time based on your oven and brownie mix instructions.

9. Add the Marshmallow Topping:

   • Remove the brownies from the oven and immediately layer additional halved S’moreMallows (use about 10–12 halves, or to taste) over the warm brownie surface.

   • Set the oven to broil and place the brownies under the broiler for 30 seconds–2 minutes, watching closely, until the marshmallows are golden brown and toasted. Do not walk away, as marshmallows burn quickly.

10. Cool and Slice:

    • Remove from the oven and let the brownies cool completely in the pan at room temperature for about 2 hours to set fully and avoid a messy cut.

    • Use the parchment overhang to lift the brownies from the pan and transfer to a cutting board.

    • Slice into 12–16 squares with a sharp knife, wiping the knife between cuts for clean edges.

Cooking Tips

• Parchment Overhang: Ensure parchment extends over the pan’s edges for easy brownie removal without sticking.

• Even Layers: Spread brownie batter carefully to cover graham crackers and marshmallows, preventing gaps in the layers.

• Watch the Broiler: Keep a close eye on the marshmallows during broiling, as they can burn in seconds; rotate the pan if needed for even toasting.

• Cool Completely: Allow full cooling to ensure the brownies hold their shape when sliced; refrigerate for 30 minutes to speed up setting if needed.