Beef Stroganoff

1 ½ lbs. beef tenderloin, top loin, or sirloin tip, well-trimmed
Season with:
Salt and ground black pepper to taste
Melt in a small saucepan over medium heat:
1 ½ tablespoons butter
Add and stir with a whisk until smooth:
1 tablespoon all-purpose flour
Add and whisk constantly to prevent lumps for 3 to 4 minutes:
1 cup beef stock, heated to a simmer
Simmer until the sauce is smooth and thickened. Set aside and keep warm. Heat in a large skillet over medium-high heat:
2 tablespoons butter
Add the beef along with:
1 onion, thinly sliced
Cook quickly, shaking the pan and stirring, until evenly browned, 1-2 minutes. The meat should remain pink in the center. Remove the meat to a warmed platter with a slotted spoon and discard the onion. Return the sauce to medium heat, stir in, and heat briefly without boiling:
3 tablespoons sour cream
1 teaspoon Dijon mustard
Salt and ground black pepper to taste
Add any accumulated juices from the cooked meat. Add the meat to the sauce and serve with hot cooked egg noodles and *sautéed mushrooms.

*Sautéed Mushrooms

Use a large skillet and give the mushrooms plenty of room so that they will brown instead of steam in their own juices.
Heat in a very large skillet over high heat:
2 ½ - 3 tablespoons butter or olive oil or a combination
Add:
1 pound any variety or combination of mushrooms, wiped clean and sliced
*TIP: Alton Brown from “Good Eats” on the Food Network suggests the following: Add the mushrooms in batches. When the first batch starts to brown, push them to the outer edges (don’t take them out) of the pan and add the second and so on. This ensures that they are all cooked well.
Cook, tossing constantly, until the mushrooms begin to color, 5-7 minutes. Season with salt and ground black pepper to taste.

NOTES:I used to make this recipe, from The Joy of Cooking, a lot when we were first married. For me, it's almost just as easy as using the cream soup style stroganoff but a whole lot tastier. When everything's cooked, we just put it all in one serving dish and mix it together.