Ingredients 1 tbsp-oil 1 tbsp-butter 1- onion thinly sliced 1/2 lbs- crimini and/or button mushrooms sliced 1 lbs-beef steak 1/4 cup- Sherry grey or sea salt salt pepper freshly ground 1/2 cup-beef stock (preferably beef bone broth) 1- bay leaf 1 tsp-horseradish mustard 1 cup-…