Heat a large, oven-safe (375°F) heavy-bottom pot or high-walled skillet (dutch oven is ideal) over medium heat.
Crisp bacon, remove and set aside. Leave the fat in the pot.
Brown the beef on all sides in bacon fat, remove, and set aside. No need to cook through, just brown.
Next fry the onion, celery, and carrots until soft. Add additional cooking oil if needed.
Add the garlic and saute for 30 seconds.
Add the tomato paste, Guinness, and Worcestershire sauce. Bring to simmer, stirring and scraping the bottom to loosen fond and incorporate into the broth.
Return the beef. Add chicken stock, thyme, and bay leaf.
Reduce to simmer: Cover and cook for 1 1/2 hours.