Instructions:

In the early versions of the recipe, mustard and Worcestershire sauce were included as an ingredient, but since the 1890's they started to be omitted in favor the rich texture of sour cream.

Ingredients

2 lbs (0.9 kg) beef tenderloin
1/2 tsp. Salt
1/4 tsp. ground white pepper
5 T (39 g) flour, divided
1 med onion, diced (shallots are even better)
8 oz (227 g) button mushrooms, cut in half
1 T (14 g) butter
4 T (57 g) demi-glace*
1 C (59 ml) beef broth
1¼ C (150 g) sour cream

Directions

Slice meat along the grain into strips 1 inch long by ¼ inch wide; season with salt and pepper. Toss in 4 T (8 g) of flour, reserving 1 T for sauce. In a large saucepan over medium high heat, cook meat until browned; transfer to a plate; set aside. Add onions and mushrooms to pan; continue cooking until light brown; transfer these to plate with meat. Add butter and remaining 1 T flour to pan, stirring constantly over low heat for 2 minutes. Stir in demi-glace, beef broth and sour cream; add salt and pepper to taste. Add meat, onions and mushrooms; heat very gently on low 15 minutes (do not simmer).

*Purchase demi-glace at Williams-Sonoma, Whole Foods or amazon.com; or reduce a high-quality beef stock or consommé.
Serving Suggestion

Serve over buttered noodles.

Prep time: 25 minutes. Cook time: 30 minutes. Makes 6 servings.