In a large Dutch oven, cook the chopped bacon over medium heat until crispy. Remove the bacon and set aside, leaving the drippings in the pot.

Season the beef cubes with salt and pepper. In the same pot, add olive oil if needed and brown the beef in batches, ensuring not to overcrowd the pan. Remove the browned beef and set aside.

Add the sliced onions to the pot and cook until softened and caramelized, about 10-15 minutes. Stir in the minced garlic and cook for an additional minute.

Sprinkle the flour over the onions and stir to combine. Cook for 2 minutes to remove the raw flour taste.

Stir in the tomato paste, thyme, and bay leaf. Gradually add the dark beer, scraping up any browned bits from the bottom of the pot.

Return the beef and bacon to the pot, then pour in the beef broth. Bring to a simmer.

Cover the pot and reduce the heat to low. Cook for 2 to 2.5 hours, or until the beef is tender. Stir occasionally and check for seasoning, adding more salt and pepper if needed.

Remove the bay leaf before serving. Garnish with fresh parsley.