
Rich and hearty, this stew is the ideal meal for a cold winter night.
Heat oil in a Dutch oven over medium-high heat. Season beef with salt and pepper. Cook, in batches, turning occasionally, until browned, 4 to 5 minutes, adding more oil if needed; transfer beef to a bowl.
Reduce heat to medium. Add onion to Dutch oven and cook, stirring occasionally, until soft, 4 to 6 minutes. Add garlic, carrots, and parsnips. Cook, stirring occasionally, until starting to soften, 3 to 5 minutes.
Sprinkle flour over vegetables and cook, stirring, 2 minutes. Add Guinness and cook, scraping up any browned bits, until starting to thicken, 1 minute. Add stock and tomato paste and stir to combine.
Add beef (and any juices), potatoes, thyme, and bay leaves. Simmer, covered and stirring occasionally, 1 1/2 hours (alternatively, transfer to a 325°F oven and bake, covered, 2 hours). Remove lid and cook, uncovered, until beef is very tender, 45 to 60 minutes (if baking, uncover and bake 45 minutes). Discard thyme and bay leaves. Season with salt and pepper. Serve sprinkled with parsley.