6 T butter
1 pound of top sirloin or tenderloin, cut thin into 1-inch wide by 2 1/2-inch long strips
1/3 C chopped onions
1/2 pound mushrooms, sliced
Salt and pepper to taste
1 C of sour cream at room temperature
Set out the sour cream so it can come to room temperature. Melt 3 T of butter in a large skillet on medium heat. Increase the heat to high/med-high and add the strips of beef. You want to cook the beef quickly, browning on each side, so the temp needs to be high enough to brown the beef, but not so high as to burn the butter. You may need to work in batches. While cooking the beef, sprinkle with some salt and pepper. When both sides are browned, remove the beef to a bowl and set aside.
In the same pan, add the rest of the butter, reduce the heat to medium and add the onions and mushrooms. Cook until tender and allowing them to soak up any meat drippings. Begin cooking the egg noodles, fettuccini is a good choice. Reduce the heat under the mushroom mixture to low and add the sour cream. Mix in the sour cream thoroughly. Do not let it come to a simmer or boil or the sour cream will curdle. Stir in the beef. Add salt and pepper to taste. Serve immediately over noodles.