Wipe beef shanks well. Thoroughly combine onion soup mix and liquid from mushrooms; stir in sliced mushrooms. Spread a small amount of mushroom mixture on top of each beef shank.

Place sliced potatoes and carrots in bottom of crockpot. Place beef shanks on top of vegetables. Pour any remaining mushroom mixture over the top. Cover and cook on low setting for 10-12 hours.

Serve with unthickened gravy poured top.