Mushroom Swiss Burgers

2 ciabatta rolls
1 Tbsp. butter
1 small onion, minced
1 clove garlic, pressed or minced
2 (4 oz.) cans sliced mushrooms
1 (10½ oz.) can Golden Mushroom soup
1 tsp. Worcestershire sauce
½ tsp. beef bouillon granules
16 oz. ground beef (85% lean)
2 green lettuce leaves
4 slices Swiss cheese

Prepare a gas or charcoal grill to medium heat. Slice the ciabatta rolls in half, horizontally, to make buns for the burgers.
Melt the butter in a medium saucepan and add the onions. Sauté the onions over medium heat, stirring often, until onions are translucent and cooked through; add the minced garlic during the last minute of cooking and continue sautéing one minute more, just until the garlic becomes fragrant. Add the canned mushrooms and allow to heat through. Add the Golden Mushroom soup, Worcestershire sauce, and beef bouillon granules and stir to combine. Reduce heat to low and allow the mushroom sauce to simmer and thicken.
Prepare the ground beef into 8 ounce patties, being sure to make them fairly large in diameter so that they will cover the entire ciabatta roll; make a small indent in the middle of each burger before placing on the grill. Sprinkle the patties with a little bit of salt, pepper, and seasoning salt just before placing on the grill and cook to desired doneness. Just before removing the burgers from the grill, place two slices of Swiss cheese on top of each hamburger patty and place the ciabatta rolls on the grill, cut sides down, to toast slightly.
Arrange the lettuce on top of the bottom pieces of the ciabatta rolls. Lay the cheese-covered hamburger patty on top of the lettuce leaf, spooning the mushroom mixture over the top of the burger, and cover with the top of the roll. Yield: 2 large cheeseburgers