In the same skillet, melt the butter. Add the chopped onions and sliced mushrooms, and sauté until the onions are translucent and the mushrooms have released their moisture and are beginning to brown.
Add the minced garlic and cook for another minute until fragrant.
Pour in the beef broth, scraping up any browned bits from the bottom of the skillet.
Stir in the Worcestershire sauce and thyme. Bring the mixture to a simmer.
Return the browned beef to the skillet. Reduce the heat to low, cover, and simmer for about 1 to 1.5 hours, or until the beef is very tender.