1. Combine oil, soy sauce, garlic powder, and pepper in a large resealable bag. Using the tip of a sharp knife, lightly score a crosshatch pattern on both sides of mushroom caps. Add to bag and toss gently until mushrooms are well coated; let sit 10 minutes, tossing occasionally.
2. Meanwhile, heat grill to high, then clean and oil grates. Leaving primary burner on high, lower other burner(s) to medium-low to set up two cooking zones.
3. Cook mushrooms on cooler side of grill, covered, until tender, 20 to 25 minutes. Flip and transfer to hotter side of grill, then cook until mushrooms are well marked, about 1 minute. Flip again and top each cap with a slice of cheese. Add rolls to cooler side of grill and cook, covered, until cheese is melted and rolls are warmed through, about 2 more minutes.
4. Spread chipotle mayo on rolls, then top with mushrooms and fried onions. Serve with additional toppings on the side.
Hannaford fresh Magazine, May-June 2022