This is what we always had a day or so after the prime rib, if there were any leftovers. My mom made it with cream. I prefer the sour cream.
1 or 2 onions, chopped
2 cups or so sliced leftover roast beef (I slice it into strips)
About 1/2 teaspoon each: marjoram and thyme
Some leftover gravy, about a cup if you have it
Large basket of fresh mushrooms or 2 three-ounce packages dried mushrooms, rehydrated
Dash of fresh nutmeg
Butter for sautéing
1/2 pint of sour cream
salt & pepper
Large flat noodles
Sauté onions until transparent. Separately sauté mushrooms and add a little grated nutmeg to them as they cook. Combine meat, onions, herbs, gravy and mushrooms in large skillet. Stir over heat until hot. Add sour cream last and take off heat as soon as it is hot. If you don’t have everything else ready, hold off on adding the sour cream. It seems to separate if it sits over heat for very long. Taste for seasoning. Serve immediately over buttered noodles.
I recently did this without having the leftover gravy. I dredged the meat in a little flour, cooked it a bit with the onions.
I used dried mushrooms, strained the water from reconstituting the mushrooms through a coffee filter, added a little beef essence, reduced it by half and added it to the meat and onions.
Comment: Dry mushrooms have so much more flavor--very concentrated--than fresh.