Pat the beef dry and season with salt and pepper.

Heat olive oil in a large heavy pot or Dutch oven over medium-high heat.

Brown the beef in batches, 2–3 minutes per side, until well-seared; transfer to a plate.

Reduce heat to medium. Add the chopped onion and cook until translucent, about 4–5 minutes. Add garlic and cook 30–60 seconds.

Stir in tomato paste and cook for 1 minute to deepen its flavor.

Pour in the stout (if using) to deglaze the pan, scraping up browned bits with a wooden spoon. Let it reduce for a minute.

Return beef to the pot. Add beef broth, thyme, and rosemary. Bring to a gentle simmer.

Reduce heat to low, cover partially, and simmer for 1.5–2 hours, or until the beef is fork-tender.

Add carrots and potatoes and continue simmering uncovered for another 20–30 minutes, until vegetables are tender and the broth has slightly reduced.

Taste and adjust salt and pepper. If you want a thicker stew, mash a few potato pieces against the side of the pot or stir in a light cornstarch slurry and simmer for an additional 2–3 minutes.

Let the stew rest for 5–10 minutes before serving.