In a large sealable bag place flour & seasonings and shake to mix. Put beef cubes in and shake to coat each piece evenly. Remove from bag and shake off any loose flour.
Put 2 T oil in large skillet on med-hi heat and add 1/2 of the beef cubes, sauteing until nice and brown. Remove to plate and add 2 T of oil and second 1/2 of beef and saute until brown, remove to plate.
While beef is frying, whisk the beef broth, mushroom soup and milk together. Set aside.
Saute onions until just limp.
Add the beef cubes back into the skillet, with any of the juices on the plate.
Add can of mushrooms.
Pour broth mixture into skillet and bring to boil, turn down heat to low, cover and simmer for about 3 hours, stirring occasionally.
If gravy is too thin, use cornstarch and water mixed together and pour slowly into the gravy while stirring.