In a measuring cup or small bowl, combine chipotle peppers and their sauce, miso, vegetable oil, and brown sugar, and mix well. Reserve 1 tablespoon of the marinade in another bowl and set aside.
Line a work surface with paper towels. Arrange tofu slices in a single layer on paper towels and cover with another layer of paper towels. Press gently to blot dry.
Place tofu in a large container, pour marinade over tofu, and gently turn to evenly coat. Refrigerate tofu at least 1 hour and up to overnight.
Stir sesame oil and soy sauce into reserved marinade and set aside.
When you’re ready to cook the tofu, prepare your grill. Light one chimney full of charcoal. When all the charcoal is lit and covered with gray ash, pour out and arrange coals on one side of the charcoal grate. Set cooking grate in place, cover grill, and allow to preheat for 5 minutes.
When your grill is hot, clean and oil the grilling grate.
Place tofu slices over the cooler side of the grill, away from the coals. Cover and cook for about 10 minutes. Carefully flip tofu and grill until browned and crisp, about 10 minutes more. Transfer to a large plate.
Using a spoon or brush, coat each piece of tofu on both sides with the reserved marinade mixture. Sprinkle scallions on top and serve right away.