Blue Cheese Hamburger

Name: Blue Cheese Hamburger
Prep time: 15 min
Cook time: 30 min
Total time: 45 min
Yield: 4
Ingredients: Ingredients; 5 lbs ground beef (80/20 blend); 4 brioche hamburger buns; 4 oz blue cheese, crumbled; 2 large yellow onions, thinly sliced; 3 tablespoons butter; 2 tablespoons brown sugar; 2 tablespoons balsamic vinegar; 4 tablespoons olive oil, divided; 2 cloves garlic, minced; Salt and black pepper to taste; 1 teaspoon garlic powder; 1 teaspoon onion powder; 1/2 teaspoon smoked paprika; 1/2 teaspoon salt; 1/2 teaspoon black pepper; 4 butter lettuce leaves (optional); 2 tablespoons mayonnaise (optional)