Preheat Oven and Prepare Pan

• Preheat the oven to 350°F (175°C).
• Line a 9×13-inch baking pan with parchment paper, ensuring it covers the edges for easy removal.
• Arrange the graham crackers in a single layer to completely cover the bottom of the pan. Break crackers as needed to fit.

2. Make the Toffee

• In a medium saucepan over medium heat, melt the butter and brown sugar together.
• Stir frequently until the mixture comes to a boil, then let it boil for 3-4 minutes, stirring continuously until thickened.

3. Assemble the Base

• Pour the hot toffee mixture evenly over the graham crackers, spreading it with a spatula to ensure full coverage.

4. Bake the Base

• Bake in the preheated oven for 6-8 minutes, or until the toffee is bubbling and slightly darkened.

5. Add Chocolate and Marshmallows

• Remove the pan from the oven and immediately sprinkle the chocolate pieces over the hot toffee.
• Let the chocolate sit for 1-2 minutes to soften, then spread it evenly with a spatula.
• Sprinkle the mini marshmallows evenly over the top.

6. Broil to Toast Marshmallows

• Turn on the broiler setting of your oven.
• Place the pan back in the oven for 1-2 minutes, watching closely, until the marshmallows are golden brown and toasty.

7. Cool and Serve

• Let the dessert cool at room temperature for 10 minutes, then transfer to the refrigerator for an additional 20-30 minutes to set.
• Once firm, break or cut into pieces and serve.