Add the mushrooms, beef broth, white cooking wine, garlic, onion, Worcestershire sauce, Dijon mustard, thyme, salt and pepper to the crockpot and stir until combined.
8 oz mushrooms, 1 cup beef broth, ¼ cup white cooking wine, 3 cloves garlic, 4 tbsp Worcestershire sauce, 2 tbsp Dijon mustard, 1½ tsp dried thyme, salt and pepper, ½ medium white onion