For the buttered egg noodles: Bring a large pot of water to a boil. Add the egg noodles and cook according to the package instructions. Drain and set aside.
For the beef stroganoff: Heat 1 tablespoon olive oil in a skillet over medium-high heat. Season the meat with salt and pepper. Add half the meat to the pan and brown it quickly. Remove the first batch and cook the rest of the meat. Remove and set aside with the first batch.
Add the remaining 1 tablespoon olive oil to the skillet and cook the mushrooms, carrots and onions until lightly browned. Turn off the heat and add the brandy and 2 cups of the stock. Turn the heat back on and reduce the liquid for 2 to 3 minutes. Mix the cornstarch with the remaining 1/4 cup stock, getting out all the lumps. Pour the slurry into the skillet and cook until the sauce thickens.
Turn off the heat. Stir in the sour cream, mustard and beef. Taste and adjust the seasoning with salt and pepper.
To finish the noodles, melt the butter in a skillet over medium heat. Add the cooked egg noodles and toss to heat through and coat with the butter.
Serve the stroganoff with the noodles, and sprinkle with the parsley.