Ingredients
- 2 Tbsp. olive oil, divided
- 2 onions (5 oz. each), cut lengthwise in half then crosswise into 1/4-inch thick slices
- 2 Tbsp. balsamic vinegar
- 1/4 tsp. plus 1/8 tsp. salt, divided
- 8 oz. mixed mushrooms*, trimmed and finely chopped
- 2 cloves garlic, minced
- 2 tsp. chopped fresh thyme
- 1 tsp. grated lemon zest
- 1 lb. ground veal
- 4 egg twist rolls, split
- 4 Boston lettuce leaves
- 4 slices thinly sliced provolone cheese
Instructions
- In 10-inch non-stick skillet over medium heat, in 1 Tbsp. hot olive oil, cook onions 7 to 8 minutes or until browned and almost tender, stirring occasionally. Add vinegar and 1/8 tsp. salt. Reduce heat to low; cover and cook 3 to 5 minutes or until tender; set aside.
- In 10-inch skillet over medium-high heat, in remaining 1 Tbsp. hot olive oil, cook mushrooms 2 minutes, stirring frequently. Add garlic, thyme and lemon zest and cook 2 minutes or until mushrooms are tender; cool.
- In bowl, mix ground veal, mushroom mixture and remaining 1/4 tsp. salt. Shape into four 3/4-inch-thick patties.
- Prepare a charcoal or gas grill or use a grill pan on top of stove over medium heat. Place rolls, cut-side down on grill; lightly toast. Remove rolls. Grill burgers 10 to 14 minutes, turning once or until internal temperature of 160° F. Place roll bottoms on serving platter. Top each bottom with lettuce leaf. Place burger on top of lettuce. Top each burger with sliced cheese, some balsamic onions and roll tops.
