Au jus gravy mix is a seasoning mix that is used to make a light gravy that is typically served with roast beef or French dip sandwiches. It is a combination of spices, bouillon, and cornstarch that is mixed with water and heated to create a flavorful sauce. The McCormick brand is a popular option for au jus gravy mix, but it can also be made at home using a recipe that includes beef bouillon cubes, onion powder, parsley, black pepper, garlic powder, and cornstarch. The homemade version is gluten-free and can be used in a variety of dishes, including soups, stews, and pot roasts.