Caramelized Onions and Blue Cheese Burgers Recipe

Onions:
2 tablespoons olive oil
2 large red, Spanish or sweet onions, thinly sliced
2 garlic cloves, minced or thinly sliced
1 tablespoon fresh rosemary
1/2 teaspoon kosher salt

Burgers:
1 1/2 to 1 3/4 pounds ground chuck
3 ounces blue cheese, crumbled, plus extra for topping
1/2 teaspoon kosher salt
1/2 to 1 teaspoon coarsely ground black pepper

1. To prepare onions, heat oil in a large skillet over low heat. Add remaining ingredients. Cook, stirring occasionally, until onions are deeply browned and slightly gooey, about 40 minutes. If onions dry out, add water, 1 tablespoon at a time. Use immediately or cover and refrigerate up to 2 days. Makes 3/4 to 1 cup.
2. To prepare burgers, divide meat into 4 balls of equal size. Divide blue cheese into 4 equal portions. Using your thumb of the back of a tablespoon, make a shallow hole in each beef portion; fill with blue cheese. Shape burger and carefully seal the opening. Form each into a patty about 3/4- to 1-inch thick. To ensure more even cooking, make a 1/2-inch indentation with your thumb in the center of the burger. Handle as little as possible.
3. Prepare grill to medium-high. Brush grill grate with oil.
4. Sprinkle both sides of the burgers with salt and pepper. Place on the grate and grill until well seared on both sides, about 5 minutes for medium-rare or 6 minutes for medium. Top with a few crumbs of cheese and let melt.
5. If cooking indoors, place a cast-iron skillet over high heat. Add burgers to dry pan. Cook until well seared on both sides, 8 to 10 minutes for medium-rare or 10 to 12 minutes for medium.

Recipe adapted with permission from Recipe of the Week: Burgers by Sally Sampson (Wiley, 2008)

Nutritional facts per serving (without bun and toppings): 320 calories,19g fat, 30g protein., 8g carbohydrates, 1g fiber, 850mg sodium.