Step 1: Brush or scrape the grill grate clean; there’s no need to oil it. Set up your grill for indirect grilling and heat slowly to medium-high. Gradually heat the salt slab at the same time.
Step 2: Lay the slivered mint leaves atop the brownies or sprinkle the brownies with creme de menthe, if using. Lay a square of chocolate on top, and top with a marshmallow.
Step 3: Arrange the marshmallow-topped brownies on the hot salt slab. Add the wood chips to the coals or to your grill’s smoker box and lower the lid. Smoke-roast the s’more brownies until the marshmallows are sizzing and browned, 6 to 10 minutes. Transfer to plates or bowls or serve them right off the salt slab, sprinkled with flaky salt, if using.
Tip – Warning
Do not make this recipe in cold weather. Hot salt slabs have been known to crack or explode when exposed to cold air.