In small saucepan mix Au Jus Sauce or broth and soy sauce; heat and keep warm.
For each serving, to order: Season 1 steak with salt and pepper, and coat with 1 tablespoon oil. Grill or pan-fry to desired doneness, turning once. Top with 1/4 cup onions and cover with 1 1/4 ounces cheese. Place in salamander. Melt and brown cheese lightly. Plate steak. Ladle 3 tablespoons au jus mixture over steak. Garnish with 1 tablespoon chives.
To make Au Jus Sauce: Heat 1 quart beef stock, 2 cups roast beef pan juices, 1 cup water and 1 cup soy sauce. (Yield: 2 quart)
To make Caramelized Onions: Thinly slice 4 pounds Spanish onions. Melt 8 ounces butter in large sauté pan. Add onions, 2 ounces minced garlic and 1/2 teaspoon black pepper. Cook over medium heat, stirring often, until onions are browned and soft. Mix in 2/3 cup soy sauce. Keep hot. (Makes about 6 cups)