Crockpot Beef with garlic

1 1/2 lbs stewing beef 1 tablespoon prepared mustard 1 tablespoon taco seasoning 1/2 teaspoon salt 1/4 teaspoon pepper 2 garlic cloves , minced 1 (16 ounce)[...]

2 lbs cubed beef stew meat 2 (10 ounce) cans condensed golden mushroom soup (do not use cream of mushroom) 1 (10 ounce) can onion soup (or 1/2 pkg dry onion[...]

1 large onion , halved and sliced thin 8 ounces portabello mushrooms , sliced 2 tablespoons butter 1 tablespoon oil 1 tablespoon flour 3 garlic cloves ,[...]