Trim any excess fat from the round steak and reserve.

Cut the steak across the grain into thin strips.

In a skillet, heat the reserved fat until you have about 3 tablespoons of melted fat.

If necessary, add butter to achieve this amount.

Remove any excess fat trimmings.

Brown the sliced steak in the skillet.

Add the sliced mushrooms with their liquid to the skillet.

Stir in the dry onion soup mix and 2/3 cup of water.

Heat the mixture to boiling.

In a small bowl, blend the sour cream and flour until smooth.

Add the sour cream mixture to the hot beef and mushroom mixture in the skillet.

Cook and stir until the sauce thickens slightly.

The sauce will be thin but flavorful.

Serve the beef stroganoff over rice or noodles.