Combine first 5 ingredients in a bowl. Shape into 4 oblong patties. Brown in a non-stick skillet, turning to brown both sides. (I use an electric skillet).
Add enough water to reserved mushroom juice to make 1 cup, if using. Mix with gravy mix and pour over patties in pan. (I like a lot of gravy so I use 2 pkgs. Be sure to double your liquid if you are making extra gravy.) Add mushrooms, if using. Stir gently as not to break the patties.