London Broil with Mushroom Sauce

Combine 1/2 cup shallots, 1 tablespoon garlic, 1 table­­spoon oil, vinegar, mustard, Worcestershire, hot sauce, and thyme in a large bowl, stirring with a whisk. Add beef, turning to coat. Refrigerate 3 1/2 hours, turning occasionally. Let beef mixture stand at room temperature 30 minutes before cooking.

Preheat broiler to high. Place oven rack 4 inches from broiler.

Heat a large nonstick skillet over medium-high heat. Add remaining 1 tablespoon oil to pan; swirl to coat. Add remaining 1/4 cup shallots, remaining 1 tablespoon garlic, and mushrooms to pan; cook 10 minutes or until mushrooms are browned, stirring occasionally. Stir in 1/4 teaspoon salt and 1/4 teaspoon pepper. Combine 1/4 cup stock and flour in a small bowl, stirring with a whisk. Add flour mixture and remaining 1 1/4 cups stock to pan; simmer 4 minutes or until slightly thickened. Remove pan from heat; stir in butter and soy sauce. Keep warm.

Remove beef from marinade; discard marinade. Wipe any marinade from beef with a paper towel. Sprinkle beef with remaining 1/2 teaspoon salt and remaining 1/4 teaspoon pepper. Place a wire rack on a jelly-roll pan. Add beef to rack. Broil 5 minutes on each side for medium-rare or until desired degree of doneness. Place beef on a cutting board; let stand 5 minutes. Cut across the grain into thin slices. Serve with mushroom mixture.