Preheat oven to 350 degrees F (175 degrees C).

In a large bowl, toss the beef with the flour, salt, and pepper until evenly coated.

Heat the olive oil in your Dutch oven over medium-high heat.

Cook the bacon until crisp. Remove to a paper towel-lined plate, reserving the fat in the pot.

Brown the beef in batches (about 3-4 batches for 3 pounds) in the bacon fat, allowing space between pieces. This takes patience but creates the foundation for incredible flavor.

Remove the browned beef and set aside.

Add the onions to the pot and cook until softened, about 5 minutes.

Add the garlic and cook until fragrant, about 1 minute.

Pour in the Guinness, scraping up any browned bits from the bottom of the pot with a wooden spoon.

Let the Guinness reduce slightly (about 2 minutes), then stir in the beef broth, Worcestershire sauce, thyme, and bay leaves.

Return the beef and bacon to the pot.

Bring the stew to a boil, then reduce heat to low, cover, and simmer for 2 hours, or until the beef is very tender.

Add the potatoes and carrots. Simmer for 1 more hour, or until the potatoes are tender but still hold their shape.

Remove the thyme sprigs and bay leaves.

Season with additional salt and pepper to taste.

Stir in the parsley just before serving.

Serve hot with crusty bread.