Pat the beef chuck cubes completely dry with paper towels, then season generously with salt and pepper. Heat 1 tablespoon of olive oil in a Dutch oven over medium high heat until shimmering.
Working in two or three batches so you don't crowd the pot, sear the beef on all sides until deeply browned, about 3 to 4 minutes per batch. Transfer the browned beef to a plate and set aside.
Add the chopped bacon to the same pot and cook over medium heat until crisp, about 5 minutes.
Add the diced onion, carrots, and celery to the pot with the bacon and its rendered fat. Cook, stirring occasionally, until the vegetables begin to soften, about 5 to 6 minutes.
Stir in the minced garlic and cook for 30 seconds more, just until fragrant.
Sprinkle the flour over the vegetables and stir constantly for about 1 minute to cook off the raw flour taste. Stir in the tomato paste and cook for another minute so it darkens slightly and deepens in flavor.
Pour in the Guinness, scraping the bottom of the pot with a wooden spoon to release any browned bits stuck to the pan. Let the beer bubble for about 2 minutes to cook off some of the sharp alcohol taste.
Return the browned beef and any accumulated juices to the pot. Pour in the beef broth and Worcestershire sauce, then add the bay leaves and dried thyme.
Stir everything together, bring to a gentle boil, then reduce the heat to low. Cover the pot and let the stew simmer gently for 1.5 hours, stirring occasionally so nothing sticks to the bottom.
After the stew has simmered for 1.5 hours, stir in the Yukon gold potato chunks. Cover again and continue simmering for another 45 minutes to 1 hour, until the potatoes and beef are both fork tender.
Check the stew occasionally and add a splash more beef broth if it looks like it's reducing too much.
Remove the bay leaves from the pot and discard them. Taste the stew and adjust the seasoning with more salt and pepper if needed.
Ladle the stew into bowls and sprinkle with chopped fresh parsley before serving.