Preheat the Oven:
Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper to make it easy to remove the bars once they are done baking.
Prepare the Crust:
In a large bowl, combine the graham cracker crumbs, cocoa powder, powdered sugar, and melted butter. Stir until the mixture has the texture of wet sand. Press the mixture firmly into the bottom of the prepared pan to form the crust. Make sure it’s even and compact to support the toppings.
Add the Sweetened Condensed Milk:
Pour the sweetened condensed milk evenly over the graham cracker crust, using a spatula to smooth it out into an even layer.
Layer the Toppings:
Sprinkle the mini marshmallows over the milk layer, followed by the chocolate chips. If you’re using chopped nuts (walnuts or pecans), sprinkle them over the top as well. This will add a delicious crunch to balance out the gooey layers.
Bake the Bars:
Bake for 25–30 minutes, or until the edges are golden and the marshmallows are just beginning to toast. Keep an eye on them to ensure the marshmallows don’t burn!
Cool and Slice:
Let the bars cool completely before slicing. This is the hardest part (trust me!), but it’s worth the wait. Once cooled, use the parchment paper to lift the bars out of the pan and slice them into 16 squares.
