To elevate his French dip sandwich, celebrity chef Bobby Flay adds dried porcini mushrooms to the jus, in which the steak-and-cheese-on-French-bread sandwich is dipped.

Au jus sauce is typically drippings left over from roasting the beef, but Flay’s version swaps the drippings for beef broth and adds porcini mushrooms, garlic, onion, and rosemary.

Porcini mushrooms are known for their rich, umami flavor and meatiness. For Flay’s French dip recipe, the mushrooms deepen the broth’s savoriness and add an earthiness to the dish.

Flay uses dried porcini mushrooms, as they impart a much deeper mushroom flavor than fresh ones. After the jus cooks down, Flay throws it into a blender and strains out the solids.