2 tablespoons vegetable oil
Salt, pepper to cover beef
1 pinch sweet paprika
1¼ pounds beef tenderloin, cut into thin, 1-inch strips
½ cup unsalted butter
10 ounces small white mushrooms, quartered
5 medium yellow onions, thinly sliced
4 large garlic cloves, minced
2 tablespoons tomato paste
3 tablespoons all purpose flour
1 cup dry white wine
2 cups water
3 tablespoons sour cream
1 tablespoon Dijon mustard
2 tablespoons freshly squeezed lemon juice
2 tablespoons chopped flat-leaf parsley
2 tablespoons chopped chives
In a large skillet over a high heat, heat one tablespoon of vegetable oil. Season half the portion of beef with salt, pepper and paprika, then flash fry very quickly so that the beef is browned but still pink in the center. Transfer to a plate and repeat with the remaining olive oil, seasonings and beef.
Return skillet to heat and add the half cup of butter. When it's just starting to brown, add mushrooms and onions, stirring for about ten minutes until brown and soft. Add the garlic and brown gently for about two minutes, then add tomato paste and flour and cook for a further four minutes. Pour in the wine and stir for another two minutes, then add two cups of water and bring to a boil. Lower the heat and simmer for about two to three minutes until it starts to thicken, then add the sour cream, mustard, lemon juice, parsley and chives. Check seasoning and add more if needed.
Place beef and any juices back in the pan and reheat gently so as not to curdle. Serve with buttered noodles or plain steamed white rice.