01 - Pat the beef cubes dry and season thoroughly with salt and black pepper.
02 - Heat 1 tablespoon vegetable oil in a large Dutch oven or heavy pot over medium-high heat. Brown the beef cubes in batches, adding more oil as needed. Transfer browned beef to a plate.
03 - Reduce heat to medium. Add chopped onions, sliced carrots, and celery to the pot. Sauté until softened, approximately 5 minutes, then add minced garlic and cook for an additional minute.
04 - Stir in the flour and cook, stirring constantly, for 2 minutes to form a roux.
05 - Mix in tomato paste thoroughly. Return the browned beef along with any accumulated juices to the pot.
06 - Pour in the alcohol-free stout and beef stock, scraping the bottom of the pot to loosen browned bits for enhanced flavor.
07 - Stir in Worcestershire sauce, brown sugar, bay leaves, and dried thyme to evenly distribute seasonings.
08 - Bring the mixture to a boil. Reduce heat to low, cover, and simmer gently for 1 hour and 30 minutes, stirring occasionally.
09 - Add the peeled, chunked potatoes. Continue simmering uncovered for an additional 30 minutes, until both beef and vegetables are tender and the stew has thickened.
10 - Remove bay leaves, adjust seasoning with additional salt if needed, and garnish with chopped fresh parsley before serving hot.