Heat the olive oil in a large Dutch oven over medium-high heat. Add the beef cubes and brown them on all sides, working in batches if needed to avoid crowding.
Lower the heat to medium and add the onion. Cook until the onion softens, then stir in the garlic and cook for one minute more.
Pour in the Guinness stout and scrape the bottom of the pot to release any browned bits. Stir in the tomato paste and thyme.
Add the beef broth, salt, and pepper. Bring the mixture to a simmer, then cover and cook for 45 minutes.
Stir in the potatoes, beets, and carrots. Continue simmering uncovered for 30 to 40 minutes until the vegetables are tender and the beef is soft.
Taste and adjust seasoning if needed. Ladle into bowls and top with chopped parsley before serving.