S'mores Bars

Method

1. Preheat the oven to 350 F and line a 9x13 inch metal baking pan with foil or parchment, leaving an overhang on two sides so you can lift the bars out later.
2. In a medium bowl, stir the graham cracker crumbs, sugar, and salt together, then pour in the melted butter and stir with a fork until the mixture looks like wet sand and every crumb is coated.
3. Press the crumb mixture firmly and evenly into the bottom of the prepared pan using the flat bottom of a measuring cup, packing it tightly so the crust holds together when sliced.
4. Bake the crust for 10 minutes, until the edges look very lightly golden, then remove from the oven (leave the oven on).
5. Immediately scatter the milk chocolate chips evenly over the hot crust and let them sit undisturbed for 2 minutes to soften, then spread them into an even layer with an offset spatula or the back of a spoon.
6. Cut the large marshmallows in half with kitchen scissors (spray the blades with a little nonstick spray first so they do not stick) and arrange the halves cut-side down over the chocolate layer, packing them close together; scatter the mini marshmallows into any gaps.
7. Return the pan to the oven and bake for 6 to 8 minutes, watching closely, until the marshmallows are puffed and golden brown on top; if you want deeper toasting, switch the oven to broil for the last 30 to 60 seconds and watch constantly so they do not burn.
8. Cool the pan completely on a wire rack for at least 1 hour at room temperature before slicing, since the chocolate layer needs to firm back up or the bars will ooze apart.
9. Lift the bars out of the pan using the foil or parchment overhang, transfer to a cutting board, and cut into 12 squares with a sharp knife, wiping the blade clean between cuts for neat edges.