Heat oil in a large skillet or Dutch oven over high heat. Season roast liberally with salt and pepper and brown beef on all sides, 4-5 minutes per side.
Transfer roast to slow cooker and add onions, mushrooms, and garlic.
Stir together beef broth, Dijon mustard, Worcestershire sauce, and thyme and add to slow cooker.
Cover and cook on high for 4 hours or low for 8 hours.
Remove roast and break apart with two forks.
Return meat to slow cooker, along with egg noodles and sour cream and stir to combine. Cover and cook on high 15 minutes.
Adjust seasoning to taste, serve, and enjoy!
