01 - In a large bowl, combine the beef cubes with all-purpose flour, kosher salt, and freshly ground black pepper, ensuring the beef is evenly coated.
02 - Heat 1 tablespoon of vegetable oil and 1 tablespoon of unsalted butter (or dairy-free margarine) in a large Dutch oven or heavy pot over medium-high heat. Brown half of the seasoned beef, turning to sear all sides for approximately 5 minutes. Transfer the seared beef to a plate and repeat the process with the remaining oil, butter, and beef.
03 - Add the chopped onions, minced garlic, diced celery, sliced carrots, and sliced parsnips to the pot. Sauté for 5 minutes until the vegetables begin to soften, scraping up any flavorful browned bits from the bottom of the pot.
04 - Stir in the tomato paste and cook for 1 minute, allowing it to deepen in color and flavor.
05 - Pour in the alcohol-free stout, thoroughly scraping the bottom of the pot to deglaze and incorporate all the flavorful fond. Add the low-sodium beef stock, Worcestershire sauce, brown sugar, bay leaves, and fresh thyme sprigs. Return all the seared beef and any accumulated juices to the pot.
06 - Bring the stew to a gentle simmer. Cover the pot and reduce the heat to low, allowing it to cook for 1 hour.
07 - Add the quartered baby potatoes, stir gently, and continue simmering uncovered for an additional 1 hour, or until the beef and vegetables are exceptionally tender and the stew's sauce has naturally thickened.
08 - Carefully remove and discard the bay leaves and thyme stems from the stew. Taste and adjust the seasoning with salt and pepper as needed.
09 - Serve the Guinness-style beef stew hot, optionally garnished with fresh chopped parsley.