Step 1

Sour cream can curdle if added directly to hot liquid. To prevent curdling, temper the sour cream by stirring a little of the hot liquid into it and then adding the warmed sour cream mixture to the pan. Buttered egg noodles are the classic accompaniment to this recipe. Add noodles to boiling water at the same time the onion goes into the pan in step 4, so that the noodles and stroganoff will be done at about the same time.

Step 2

Heat 1 tablespoon oil in heavy-bottomed 12-inch skillet over medium-high heat until hot and shimmering, but not smoking, about 2 minutes; swirl to coat pan. Add mushrooms and cook over high heat without stirring for 30 seconds; season with salt and pepper and continue to cook, stirring occasionally, until mushrooms are lightly browned, about 4 minutes longer. Transfer to medium bowl.

Step 3

Return skillet to high heat, add remaining 1/2 tablespoon oil; swirl to coat pan. Place tenderloin strips in skillet. Using tongs, spread the meat into single layer, making sure that strips do not touch, and cook without turning until well-browned on first side, 2 minutes. Turn strips and cook on second side until well-browned, about 1 minute longer. Season with salt and pepper to taste and transfer to bowl with mushrooms.

Step 4

Add beef broth to skillet, scraping up browned bits on pan bottom with wooden spoon; simmer until broth is reduced to 1/4 cup, about 3 to 4 minutes. Transfer broth to bowl with mushrooms and beef, scraping skillet clean with rubber spatula.

Step 5

Return skillet to medium-low heat and add butter; when butter foams, add onion, tomato paste, and brown sugar. Cook, stirring frequently, until onion is lightly browned and softened, about 6 minutes; stir in flour until incorporated. Gradually whisk in chicken broth and wine; increase heat to medium-high and bring to boil, whisking occasionally, then reduce heat to medium-low and simmer until thickened, about 2 minutes. Whisk liquid from mushrooms and beef into sauce and simmer to incorporate. Stir about 1/2 cup of hot sauce into sour cream, then stir mixture back into sauce. Add mushrooms and beef; heat to warm through, about 1 minute. Adjust seasonings with salt and pepper and serve over buttered egg noodles.