Pat the beef cubes dry with paper towels. Combine kosher salt and black pepper and sprinkle evenly over the beef. Place the flour in a shallow bowl or tray and toss or lightly dredge the beef cubes so each piece has a light coating of flour; shake off excess.

Brown the beef

Heat a large Dutch oven or heavy-bottomed pot over medium-high heat. Add 2 tablespoons of neutral oil and let it heat until shimmering. Work in batches to avoid crowding: add beef cubes in a single layer and brown on all sides, about 3–4 minutes per batch. Transfer browned beef to a plate and repeat, adding the remaining 1 tablespoon oil as needed. You want a deep brown crust for flavor. Set all browned beef aside.

Aromatics and vegetables

Reduce heat to medium. If the pot is dry, add the remaining 1 tablespoon of oil. Add diced onion, carrots, and celery. Cook, stirring occasionally, until softened and starting to brown, 6–8 minutes. Add minced garlic and cook 30–45 seconds until fragrant. Stir in the tomato paste and cook 1–2 minutes, stirring frequently, until the paste caramelizes slightly and darkens — this builds sauce depth.

If there are browned bits stuck to the bottom of the pot (fond), deglaze in the next step with wine or stock, scraping them up with a wooden spoon — these are important for flavor.

Sauce liquids and seasoning

Increase heat to medium-high. Pour in the red wine to deglaze the pot, scraping up any browned bits; let the wine reduce by about half, 2–3 minutes. If not using wine, add 1 cup beef stock instead and scrape the fond.

Add the remaining beef stock, Worcestershire sauce, soy sauce, brown sugar, dried thyme, and bay leaves. Stir to combine. Return the browned beef and any accumulated juices to the pot, submerging pieces in the liquid as much as possible. Bring to a gentle simmer.

Once simmering, reduce heat to low, cover partially with a lid (offset to allow some steam escape), and simmer gently until the beef is fork-tender, 1.75–2.25 hours (check at 1.5 hours). Stir occasionally, skim any excess fat if desired, and add a splash of stock if sauce reduces too much before beef is tender.

Thickening & finish

When the beef is tender and sauce has developed deep flavor, remove and discard bay leaves. Taste the sauce and adjust salt and pepper as needed. For a thicker, glossy sauce: mix cornstarch and cold water to make a slurry, then stir it into the simmering sauce a little at a time. Allow sauce to return to a gentle boil and thicken, about 2–3 minutes. Add chopped parsley and, if using, lemon juice to brighten the flavor. Stir to combine.

If you prefer a smoother sauce, remove half of the sauce and purée it with an immersion blender or in a stand blender, then return to the pot and stir to combine. Warm through for 1–2 minutes.

Serve the saucy beef hot over mashed potatoes, egg noodles, rice, or with crusty bread to soak up the sauce.