Pat the beef dry, then season with the salt and pepper.
Heat the olive oil in a large Dutch oven over medium-high. Sear beef in two batches until browned. Transfer to a plate.
Melt 1 tbsp butter in the pot. Add onion and mushrooms; cook, stirring, until lightly browned, 5–6 minutes.
Stir in garlic and thyme; cook until fragrant, about 30 seconds.
Splash in Worcestershire and soy sauce. Pour in beef broth and Dijon; scrape up browned bits.
Return beef and any juices. Bring to a lively simmer.
Stir in egg noodles. Simmer, stirring occasionally, until just tender, 8–10 minutes.
Mix cornstarch with water. Stir the slurry into the pot and simmer until the sauce thickens, 1–2 minutes.
Turn off heat. Swirl in remaining 1 tbsp butter and the sour cream. Adjust seasoning and garnish with parsley.