Slow Cooker Method:
Transfer to Slow Cooker: Place the seared beef and sautéed onions into the slow cooker.
Add Ingredients: Add the mushrooms, garlic powder, onion powder, thyme, rosemary, bouillon cube, Worcestershire sauce, bay leaf, pepperoncinis, and beef stock.
Cook: Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the beef is tender.
Thicken Gravy: About 30 minutes before serving, stir in the cornstarch slurry to thicken the gravy. Season with salt and pepper to taste.
