Spray large skillet with nonstick spray over medium heat. Add onions and meat, cooking 5 minutes until browned.
Add garlic powder, onion powder, salt, pepper, and mustard. Stir to combine.
Add Worcestershire and 1/4 cup broth. Simmer 2-3 minutes.
Mix cornstarch with remaining broth, add to meat, and simmer 5 minutes to thicken.
Make sauce: Combine mayo, ketchup, pickles and pickle juice in small bowl.
Assemble: Place bottom buns on baking sheet. Top each with 1 tbsp sauce, lettuce, 1/2 cup meat (103g), and cheese slice. Broil until cheese melts.
Add 1 tbsp sauce to top buns and assemble sandwiches.