Preheat the oven 325F then line the bottom of an 8x8 inch baking pan with parchment paper or aluminum foil, leaving an overhang on the sides for easy removal later.
Place the graham cracker sheets on the bottom of the pan in a single layer, covering the entire surface. You may need to break some of the sheets to fit them evenly.
5 graham cracker sheets
In a large bowl, mix the brownie mix, egg yolks, hot brewest coffee, vegetable oil, vanilla extract, and salt. Fold in the chocolate chips.
1 box of brownie mix, 2 egg yolk, ½ cup vegetable oil, ⅓ cup brewed hot coffee, 1 teaspoon vanilla extract, ¼ teaspoon salt, ½ cup chocolate chips
Pour the brownie batter evenly over the layer of graham crackers in the prepared pan then bake in the preheated oven for 40 minutes.
Pull the brownies out and carefully top them with the mini marshmallows. Place back in the oven and bake for another 3-4 minutes.
2 cups mini marshmallows
Remove the pan from the oven then using a kitchen torch, toast the marshmallows on top. Allow the brownies to cool down fully before slicing and enjoying. Read the notes on how to slice this dessert.