- 2 pounds beef chuck, trimmed of excess fat and cut into thin slices (about 1/2 inch thick and 3 inches long)
- 1 large onion, chopped (about 2 cups)
- 1 pound white mushrooms, trimmed and halved (or quartered, if large)
- Coarse salt and ground pepper
- 2 tbsp. cornstarch
- 1/2 c sour cream
- 2 tbsp. Dijon mustard
- Cooked thin egg noodles, for serving
- Chopped fresh dill, for garnish (optional)
- In a 5- to 6-quart slow cooker, toss beef, onion, and mushrooms with 1 1/2 teaspoons coarse salt and teaspoon pepper.
- Cover, and cook on low until meat is tender, about 8 hours (or on high for 6 hours).
- In a 2-cup glass measuring cup, whisk cornstarch with 2 tablespoons water.
- Ladle 1 cup cooking liquid into measuring cup; whisk to combine.
- Pour into a small saucepan, and bring to a boil; cook until thickened, about 1 minute.
- With slow cooker turned off, stir in cornstarch mixture, then sour cream and mustard.
- Serve beef over noodles; sprinkle with dill, if desired.