Description
Beef Stroganov,  is a blend of favorite Russian foods --fine beef, plump mushrooms, yellow onions--served in a spicy sour cream sauce and customarily strewn with crisp straw potatoes. Named after the late 19th Century of a Russian count, whose cook invented the meal, beef Stroganov has become one of the famous dishes across the world. The following recipe is the classic Russian version. The numerous European and American variations called beef Stroganov do not reproduce the dish as it was originally concieved.

Ingredients
1 tablespoon of powdered mustard
1 tablespoon of sugar, 2 teaspoons of salt
4 to 5 tablespoons of vegetable oil
4 cups of finely sliced yellow onions separated into rings
1 pound of fresh mushrooms, thinly sliced lengthwise
2 pounds of fillet of beef, trimmed of all its fat
1 teaspoon of freshly ground black pepper
1 pint of sour cream

Recipe
In a small bowl combine the mustard, 1? teaspoons of sugar, a pinch of salt and enough hot water (perhaps a tablespoon) to form a thick paste. Let the mustard rest at room temperature for about 15 minutes. Heat 2 tablespoons of the oil in a heavy 10- to 12- inch skillet over high heat until a light haze forms above it. Drop in the onions and mushrooms, cover the pan, and reduce the heat to low. Stirring from time to time, simmer 20 to 30 minutes, or until the vegetables are soft. Drain them in a sieve, discard the liquid and return the mixture to the skillet. With a large, sharp knife cut the fillet across the grain into 1/4 inch-wide rounds. Lay each round on a board and slice them with the grain into 1/4-inch-wide strips. Heat 2 tablespoons of oil in another heavy 10- to 12-inch skillet over high heat until very hot but not smoking.Drop in half the meat and, tossing the strips constantly with a large spoon, fry for 2 minutes or so until the meat is lightly browned. With a slotted spoon transfer the meat to the vegetables in the other skillet and fry the remaining meat similarly, adding additional oil if necessary. When all the meat has been combined with the vegetables, stir in the remaining salt, pepper and the mustard paste. Stir in the sour cream, a tablespoon at a time, then add the remaining 1/2 teaspoon of sugar and reduce the heat to low. Cover the pan and simmer 2 or 3 minutes, or until the sauce is heated through. Taste for seasoning. To serve the dish, transfer the contents of the pan to a heated serving platter and, if you like, scatter straw potatoes over the top.