Brown the ground beef in a large skillet until fully cooked; remove with a slotted spoon.
Cook the onion and mushrooms in the skillet until browned. Add rosemary, thyme and Dijon; season to taste.
Stir in flour and cook briefly. Deglaze with sherry, scraping up browned bits. Gradually add beef stock and simmer until thickened.
Cook egg noodles according to package directions. Turn off heat under gravy; stir in sour cream and return the beef. Toss with drained noodles and serve.