I have to tell you, this is one of my FEW specialties in cooking. I have sworn by the Joy of Cooking Beef Stroganoff recipe for 25 years, using an ancient electric skillet, and it's ALWAYS good. The recipe here is updated, but I'm sure it will suit just fine.

BEEF STROGANOFF
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4 to 6 servings
Cut into thin 2 x 1⁄ 4-inch strips:
2 pounds fillet of beef, top loin, or sirloin tip
Season with:
Salt and black pepper to taste
Heat in a large skillet over medium-high heat:
2 tablespoons olive or vegetable oil
Add the meat in batches, cooking just until browned, about 2 minutes. Remove to a plate and melt in skillet:
3 tablespoons butter
Add and cook, stirring until softened, about 3 minutes:
1 onion or 2 shallots, chopped
Add, and cook, stirring, until the liquid the mushrooms release evaporates, about 8 minutes:
1 pound mushrooms, sliced
Add:
2 cups beef broth or stock
(2 tablespoons Cognac)
Simmer about 10 minutes, then stir in:
1 cup sour cream
1 tablespoon Dijon mustard
Salt and black pepper to taste
Add any accumulated juices from the cooked meat.
Simmer—do not boil—until the meat is heated through but still medium-rare, about 2 minutes. Stir in, if desired;
(2 tablespoons chopped dill)
Serve immediately, with:
Fresh egg noodles