Bacon-Cheddar Burgers With Caramelized Onions

• 3 tablespoons extra-virgin olive oil
• 1 1/2 pounds onions (2 large), sliced into 1/2-inch-thick rings
• Salt and freshly ground black pepper
• 3 tablespoons seasoned rice vinegar
• 1/2 pound sliced bacon, frozen 1 hour
• 1 1/2 pounds ground beef chuck
• 1 tablespoon Worcestershire sauce
• Salt
• Freshly ground black pepper
• 2 tablespoons unsalted butter, melted
• 4 to 8 thin slices extra-sharp Cheddar
• 4 hamburger buns or alternatives such as kaiser or brioche rolls
• Sliced tomato
• Soft-leaf lettuce leaves or baby arugula
• An instant-read thermometer

1. Heat oil in a 12-inch heavy skillet over medium heat until it shimmers, then cook onions with 1/2 teaspoon salt and 1/4 teaspoon freshly ground black pepper, covered, stirring occasionally, until golden and softened, 15 to 20 minutes.
2. Reduce heat to medium-low, then add vinegar, scraping up the brown bits on bottom of the skillet, and cook, uncovered, stirring, until liquid evaporates, 1 to 2 minutes. Season to taste with salt and pepper. Transfer to a small bowl and keep warm, covered.
3. Prepare grill for indirect-heat cooking over medium-hot charcoal (medium heat for gas; see
4. ).
5. Meanwhile, cut frozen bacon crosswise into eight sections and distribute evenly in bowl of a food processor, then pulse until finely chopped.
6. In a large bowl, distribute bacon evenly over beef and drizzle mixture with Worcestershire sauce. Sprinkle evenly with 1 teaspoon salt and 1/2 teaspoon freshly ground black pepper.
7. Combine mixture as gently and thoroughly as possible with your fingers (be careful not to overmix). Form into 4 patties, about 4 inches in diameter and 1 inch thick.
8. Brush cut sides of buns with butter.
9. Oil grill rack, then sear patties directly over coals (or lit burner or burners), covered only if using a gas grill, moving to area of grill with no coals (or over shut-off burner) if flare-ups occur, until browned, 2 to 3 minutes on each side.
10. Move burgers to area with no coals (or over shut-off burner) and grill, covered, turning once, until they reach 155u0b0F on instant-read thermometer, about 4 minutes total. Top with cheese to taste and heat, covered, until it melts and burgers register 160u0b0F, about 1 minute. Transfer burgers to a clean platter.
11. Grill buns, buttered side down, until grill marks appear, about 1 minute.
12. Assemble burgers with buns and accompaniments, topping cheese with caramelized onions.

extravirgin olive oil, onions, salt, rice vinegar, bacon, ground beef chuck, worcestershire sauce, salt, freshly ground black pepper, unsalted butter, cheddar, buns, tomato, arugula, thermometer

Taken from www.epicurious.com/recipes/food/views/bacon-cheddar-burgers-with-caramelized-onions-51112220 (may not work)