Cremini offer deeper, richer flavor, but you can also use regular button mushrooms.
1 tablespoon olive oil
12 ounces ground sirloin
2 (8-ounce) packages presliced cremini mushrooms
1 cup prechopped onion
3 garlic cloves, minced
1/2 cup no-salt-added tomato paste
1 tablespoon minced fresh oregano
2 tablespoons red wine vinegar
2 tablespoons Worcestershire sauce
1 tablespoon molasses
1/4 teaspoon salt
3/4 teaspoon freshly ground black pepper
1/2 teaspoon hot sauce
4 (2-ounce) Kaiser rolls or hamburger buns, toasted
1. Heat a large nonstick skillet over medium-high heat. Add oil; swirl to coat. Add beef; cook for 4 minutes or until browned, stirring to crumble.
2. While beef cooks, place mushrooms in a food processor; pulse 10 times or until finely chopped. Add mushrooms, onion, and garlic to pan; cook for 3 minutes or until onion is tender. Add tomato paste and next 5 ingredients (through salt) to pan; cook 5 minutes or until mushrooms are tender and liquid evaporates. Stir in pepper and hot sauce. Spoon about 1 cup beef mixture on bottom half of each bun; top with top halves of buns.
Bruce Weinstein and Mark Scarbrough, Cooking Light