✓ Preheat the oven to 350°F (175°C) and line a 9×13‑inch baking pan with parchment paper, allowing excess to hang over the sides for easy removal.

✓ In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy, about 3–4 minutes.

✓ Add the eggs one at a time, beating well after each addition, then stir in the vanilla extract.

✓ In a separate bowl, whisk the flour, baking soda, and salt; gradually incorporate the dry mixture into the wet ingredients, mixing just until combined.

✓ Fold in the chocolate chips and graham cracker crumbs, ensuring an even distribution throughout the dough.

✓ Spread the dough evenly in the prepared pan, smoothing the top with a spatula to create a uniform layer.

✓ Place the pan in the preheated oven and bake for 12–15 minutes, or until the edges turn golden brown and a toothpick inserted near the center comes out with only a few moist crumbs.

✓ While the base bakes, lightly toast the mini marshmallows on a separate baking sheet under the broiler for 30 seconds, watching closely to avoid burning.

✓ Remove the cookie base from the oven and immediately sprinkle the toasted marshmallows over the warm surface, allowing them to melt slightly.

✓ Return the pan to the oven for an additional 2 minutes, just enough to create a lightly browned, caramelized marshmallow layer.

✓ Allow the bars to cool completely in the pan; this helps them set and makes cutting easier.

✓ Using the overhanging parchment, lift the slab onto a cutting board and slice into 12 even bars.

✓ Serve warm for a gooey experience, or store at room temperature for a firmer, chewy bite.