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.