Portobello Burgers With Blue Cheese And Sautéed Red Onions

Name: Portobello Burgers With Blue Cheese And Sautéed Red Onions
Ingredients: FOR THE PORTOBELLO BURGERS; 8 large portobello mushroom caps; 4 cloves garlic, minced; 3 tbsp. steak sauce, like A1; Â¾ cup breadcrumbs; 1 egg; Â½ tsp. fresh-ground black pepper; FOR THE ONIONS; 3 tbsp. butter; 1 large red onion, thinly sliced; 2 tbsp. balsamic vinegar; 2 tsp. dried thyme; Salt and pepper, to taste; 2 tbsp. olive oil; 4 oz. blue cheese, crumbled; 4 sesame seeded hamburger buns, split and toasted