This is a quick recipe I came up with because we were just craving a French dip style sandwich. The mushrooms could be left out, but they flavor the au jus so much I dont think I could ever leave them out!
In a large skillet, saute mushrooms in olive oil. While they are sauteeing, season with garlic, Mccormick's, salt, and pepper.
Add beef broth (reserve 1/2 a cup), worcestershire sauce, and onion.
In a small bowl, mix 1/2 cup beef broth with cornstarch. Add to the mushroom mixture. Bring to a bowl, then reduce heat and let simmer about 5 minutes.
Add roast beef to mushroom au jus and cover, simmering about 10 minutes.
Meanwhile, cut your Italian bread into 8 slices. If not already split (sandwich style) go ahead and cut them, so you have 16 total slices of bread.
Place bread on cookie sheet. On 8 of the slices (bottom slice) place about 4 or 5 pieces of roast beef on each, then spread mushrooms evenly among each sandwich. Top each sandwich with a slice of swiss cheese.
Place sandwiches in oven and broil just until cheese is melted and bread is a bit toasted, about 5 minutes.