1 Heat pasta water: Put a large pot of salted water (1 teaspoon salt for every quart of water) on to heat, for the pasta.
2 Brown the ground beef: Heat a large sauté pan on medium high heat. Melt 1 teaspoon butter in the pan and swirl it around.
Working in batches as not to crowd the meat (crowding it will make it hard to brown), break up the ground beef and add it to the pan. Sprinkle the meat with salt. Do not stir the meat, as stirring will prevent browning.
Once the meat is well browned on one side (a couple minutes, depending on how hot the pan), use tongs or a fork or a metal spatula to flip to the other side.
Once that side is browned as well, use a slotted spoon to remove from the pan and set aside.
Continue to brown the meat in batches, adding a teaspoon of butter to the pan with each batch if needed, and salting the pan and the meat, until it is all browned. Remove meat from pan. Drain excess fat from pan.
3 Sauté the onions: Add the onions to the pan. If you are working with very lean meat, you may not have any residual fat in the pan. If this is the case, you'll want to add in a tablespoon of olive oil or butter to the pan.
Cook the onions, scraping up the meat drippings, until soft, about 5 minutes. Remove onions from the pan (add to the meat).
4 Start cooking pasta: Depending on the cooking times of your particular brand of pasta, this is likely a good time to add the pasta to the (should be now) boiling, salted water.
5 Sauté mushrooms, add sherry: While the pasta is cooking, add a tablespoon of butter to the pan, increase the heat to medium high. Add the sliced mushrooms. Sauté until nicely browned (about 4 minutes).
Add the sherry (or dry white wine or water) to the pan to deglaze the pan, scraping up any browned bits. Let the sherry reduce by at least a half, then lower the heat to low.
6 Stir in sour cream, paprika, lemon juice, meat, onions, parsley: Remove the pan from the heat. Mix in the sour cream and paprika until smooth. Return the pan to very low heat, and not let the sour cream boil (or it may curdle). You may add a few tablespoons of water to the mixture to thin it out a bit at any time.
Stir in the lemon juice, and about 1/4-1/2 teaspoon of salt (taste).
Stir in the meat and onions. Stir in the chopped parsley. Add more salt, pepper, and/or paprika to taste.
7 Serve with noodles: Keep the stroganoff on warm heat until the noodles are done cooking. When the noodles are ready (al dente) drain.
Serve the hamburger stroganoff on top of egg noodles.