1. Heat olive oil in a large pot or Dutch oven over medium-high heat.

2. Add the beef cubes in batches and brown them on all sides. Remove the beef and set aside.

3. In the same pot, add the chopped onion, carrots, and celery. Cook for 5-7 minutes until softened.

4. Add the minced garlic and cook for another 1-2 minutes, stirring frequently.

5. Stir in the tomato paste and cook for 2 minutes to enhance the flavor.

6. Pour in the Guinness stout and beef broth, scraping the bottom of the pot to release any brown bits.

7. Add the browned beef back into the pot along with dried thyme, bay leaf, salt, and pepper.

8. Bring the stew to a boil, then reduce the heat and cover. Let it simmer for 1.5-2 hours, or until the beef is tender.

9. (Optional) If you prefer a thicker stew, mix 2 tablespoons of flour with a little water to make a slurry and stir it into the stew. Cook for another 10-15 minutes until thickened.

10. Discard the bay leaf, and taste for seasoning, adding more salt and pepper if needed.

11. Garnish with fresh parsley and serve hot with crusty bread.