BBQ Portobello Mushroom Burger
Combine soy sauce, balsamic vinegar, olive oil, and garlic in a large zip-top plastic bag; add mushrooms to bag. Seal and marinate at room temperature for 2 hours, turning bag occasionally. Remove mushrooms from bag and discard marinade.
Preheat grill for medium-high heat. In a medium bowl, mix together black beans, cheese, BBQ sauce, and jalapeno seeds. For a less spicy flavor, use fewer jalapeno seeds. Divide the filling equally among four mushroom caps. Place mushroom on grill, stuffing side up. Cover the grill and cook until cheese melts and juices bubble at edges of mushroom, about 6 minutes.
Serve stuffed mushroom caps on a toasted roll with your favorite condiments.