1-First Step: Prepare your baking environment. Preheat your oven to 350°F (175°C) and line a 9×13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal later. This simple preparation step prevents sticking and makes cleanup effortless. Gather all your ingredients before beginning to ensure a smooth cooking process. Having everything measured and ready makes the process enjoyable and stress-free.

2-Second Step: Create the graham cracker crust. In a medium bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Mix until the crumbs are evenly coated and the mixture holds together when pressed. Pour this mixture into your prepared pan, pressing firmly and evenly across the bottom using the bottom of a measuring cup or glass. Bake the crust for 8-10 minutes until lightly golden. This pre-baking step ensures the crust maintains its structure when adding the heavier chocolate layer.

3-Third Step: Prepare the chocolate filling. While the crust is baking, mix the chocolate chips and sweetened condensed milk in a medium bowl. Once the crust is done, carefully spread the chocolate mixture evenly over the warm crust. The heat from the crust will help melt the chocolate slightly, making it easier to spread. Return the pan to the oven and bake for 12-15 minutes, or until the chocolate layer is set and bubbling slightly around the edges.

4-Fourth Step: Add the marshmallow layer. Remove the pan from the oven and immediately sprinkle the mini marshmallows evenly over the hot chocolate filling. For extra flavor, you can add chocolate chunks or crushed graham crackers between layers. Return the pan to the oven for 3-5 minutes, watching closely to prevent burning. You want the marshmallows to be puffy and lightly golden, not browned.

5-Final Step: Complete with optional broiling. For a more toasted appearance on your marshmallows, switch your oven to broil for 30-60 seconds, keeping the pan about 6 inches from the heat source. Watch extremely carefully as marshmallows can burn quickly. Once achieved, remove from the oven and let cool completely before cutting. The bars need at least 2 hours at room temperature or 1 hour in the refrigerator to set properly. Use the parchment paper overhangs to lift the bars out of the pan, then cut into squares with a sharp knife wiped clean between cuts for the neatest appearance.