Patty Melt Casserole

2 yellow onions, diced
2 tsp. sugar
1 Tbsp. vegetable oil
1 cup mayonnaise
1/2 cup ketchup
4 Tbsp. minced dill pickles, divided
1 1/2 lbs. ground round
1 Tbsp. Worcestershire sauce
1 Tbsp. minced fresh garlic
2 tsp. black pepper
1 tsp. each kosher salt and caraway seed
2 Tbsp. flour
1 cup low sodium beef broth
6 slices marble rye bread
12 oz. shredded Swiss or cheddar cheese
1 bag frozen crinkle cut French fries, 33 oz

Preheat oven to 450. Caramelize onions with sugar in oil in skillet over medium low heat, covered, 20 to 25 minutes.Meanwhile, whisk together mayonnaise, ketchup, and 2 Tbsp. pickles for dressing.
Add ground beef, Worcestershire, garlic, pepper, salt and caraway seed to skillet increase heat to high and cook til meat is browned. Drain and discard all but 2 Tbsp. drippings.
Stir in flour, cook 3 minutes. Stir in broth and 1 cup dressing; cook to thicken into gravy.
Layer 3 bread slices in bottom of a 7 x 11 inch baking dish. Top bread with a third of the cheese, meat mixture, remaining 3 bread slices another third of cheese and French fries. Cook casserole til fries are crisp, 20 to 25 minutes.
Preheat broiler to high with rack 6 inches from element. Sprinkle remaining cheese over casserole and broil til cheese melts, 3 minutes. Drizzle casserole with some of the dressing and sprinkle top with remaining 2 Tbsp. pickles. Serve remaining dressing on the side. Serves 6