Pat the beef cubes dry with paper towels. Season evenly with kosher salt and black pepper. Place the flour in a shallow bowl or plate and toss the beef cubes in the flour to coat lightly, shaking off excess. Set aside on a tray.

Browning and Aromatics

Heat a large heavy-bottomed Dutch oven or pot over medium-high heat until hot. Add the neutral oil and butter. When the fat is shimmering, working in batches to avoid crowding, add the floured beef and brown on all sides, about 3-4 minutes per batch. Transfer browned beef to a plate and repeat until all beef is browned.

Reduce heat to medium. If the pot is dry, add a splash (about 1 tbs) of oil. Add the diced onion, carrots, and celery. Sauté until softened and beginning to brown, about 6-8 minutes. Stir in the minced garlic and cook 30-45 seconds until fragrant.

Liquids and Seasoning

Deglaze

Push the vegetables to one side and add the tomato paste to the cleared area. Cook the paste 1-2 minutes, stirring, until it darkens slightly. Pour in the red wine (or 1/2 cup beef broth if not using wine) to deglaze, scraping up browned bits from the bottom with a wooden spoon.

Return the browned beef and any accumulated juices to the pot. Add the remaining beef broth, Worcestershire sauce, bay leaves, thyme sprigs, and diced/crushed tomato if using. Bring to a simmer.

Once simmering, reduce heat to low so the liquid maintains a gentle simmer. Cover the pot partially with a lid and cook for 1.5 to 2 hours, stirring occasionally, until the beef is fork-tender. If using a slow cooker, transfer contents to the slow cooker and cook on low 6-8 hours.

Vegetables & Finishing

About 30 minutes before the end of cooking, add the potato pieces to the stew. Continue simmering, covered, until potatoes are tender when pierced with a fork (about 25-30 minutes). If the stew is too thin at any point, make a slurry by whisking the cornstarch with the water and stirring it into the simmering stew, cooking 2-3 minutes until thickened.

Five minutes before serving, stir in the frozen peas to heat through. Remove and discard bay leaves and thyme sprigs stems. Taste and adjust seasoning with salt and pepper as needed.

Stir in the chopped parsley just before serving. Serve hot with crusty bread, mashed potatoes, or over buttered noodles.