- 1 large eggplant (about 1 1/2 pounds), trimmed and sliced lengthwise into four 1/2-inch thick planks
- 1/2 cup BBQ sauce, divided
- 1 teaspoon kosher salt
- 1/2 teaspoon freshly ground black pepper
- 8 ounces cremini mushrooms, thinly sliced
- 1 red onion, halved and sliced into thin wedges
- 2 tablespoons vegetable oil
- 4 slices provolone cheese (1/8-inch thick slices)
- 4 ciabatta or hoagie rolls, split and toasted
- 1/4 cup mayonnaise
- 2 jarred pepperoncini peppers, thinly sliced
- Position oven rack six inches from the heat source and preheat broiler on high. Line broiler pan or rimmed baking sheet with foil.
- Brush eggplant slices on both sides with 2 tablespoons BBQ sauce and season with 1/2 teaspoon salt and 1/4 teaspoon peeper. Arrange slices on foil-lined pan.
- Broil eggplant until browned and soft, about 4 minutes. Meanwhile, in a medium bowl, toss mushrooms and red onion with oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper and reserve.
- Remove broiler pan from oven, flip eggplant slices, and brush with 2 more tablespoons BBQ sauce. Scatter mushroom mixture around the eggplant on the pan and broil until browned and soft, about 3 minutes more. Add 1 slice of cheese to each eggplant plank and continue to broil until cheese is melted and browned, about 2 minutes more.
- To assemble the sandwiches, brush the top toasted half of each roll with 1 tablespoon mayonnaise and each bottom half with 1 tablespoon BBQ sauce. Layer an eggplant slice, some mushroom mixture, and a few slices of pepperoncini on the bottom of each roll. Close the sandwiches and serve immediately.