Pat the beef cubes dry with paper towels. Season evenly with 1½ teaspoons salt and 1 teaspoon black pepper. Place the flour in a shallow bowl and dredge the beef cubes, shaking off excess.

Aromatics & Vegetables

Heat a large Dutch oven or heavy-bottomed pot over medium-high heat. Add 1 tablespoon vegetable oil and 1 tablespoon butter. When shimmering, brown half the beef in a single layer without crowding, about 2–3 minutes per side until deep brown. Transfer to a plate and repeat with remaining oil, butter and beef. Reserve browned beef.

Reduce heat to medium. Add the diced onion, carrots and celery to the pot. Cook, stirring occasionally, until vegetables soften and begin to caramelize, about 6–8 minutes. Add the minced garlic and cook 30–45 seconds until fragrant.

Liquids & Stock

Stir in 2 tablespoons tomato paste and cook 1–2 minutes to remove raw tomato taste. Pour in the 12 oz Guinness, scraping the browned bits from the bottom of the pan (deglaze). Let the beer simmer 2–3 minutes to reduce slightly.

Return the browned beef and any accumulated juices to the pot. Add 3 cups beef stock, 1 tablespoon Worcestershire sauce and 1 teaspoon brown sugar (if using). Add the thyme sprigs and 2 bay leaves. The liquid should come about three-quarters up the beef; add a little extra stock or water if needed.

Bring the pot to a gentle simmer, then cover and transfer to a preheated oven at 325°F (160°C), or reduce heat to low and simmer gently on the stovetop. Braise until beef is fork-tender, about 2 to 2½ hours. Check once at the 1-hour mark to ensure gentle simmer and adjust liquid if necessary.

Finishing

When beef is tender, remove the pot from oven. Skim off excess fat from the surface, remove and discard the thyme sprigs and bay leaves. If you prefer a thicker sauce, whisk together 1 teaspoon cornstarch with 2 tablespoons cold water until smooth, then stir into the simmering stew and cook on stove for 3–5 minutes until slightly thickened.

Taste and adjust seasoning with salt and pepper as needed. Sprinkle with chopped fresh parsley just before serving.