Step 1: Set up your grill for indirect grilling and heat high (450 degrees). Place the plank directly on the grill grate and grill until singed on one side. Set aside and let cool. (This step is optional, but it gives you a lot more flavor.) Arrange the brownies on the charred side of the plank.
Step 2: Lay the slivered mint leaves atop the brownies. Sprinkle with Grand Marnier (if using). Lay a rectangle of chocolate on top, and top with a marshmallow.
Step 3: Place the plank with the brownies on the grill grate. 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 sizzling and browned, 6 to 8 minutes, or as needed. Transfer to plates and serve at once–scoops of ice cream optional.
Our thanks to the sponsors of Project Fire Season 1:
Steven Raichlen’s Project Fire is a production of Maryland Public Television, Barbacoa, Inc., and Resolution Pictures. © 2018 Barbacoa, Inc.