01 - Pat beef cubes thoroughly dry with paper towels. Toss beef with flour, salt, and pepper in a large bowl until evenly coated.
02 - Heat vegetable oil in a large Dutch oven over medium-high heat. Add beef in batches, searing on all sides until deeply browned. Transfer browned beef to a plate and repeat until all beef is cooked.
03 - Reduce heat to medium. Add chopped onions to the pot and cook for 3 minutes until softened and translucent. Add minced garlic and cook for 1 minute until fragrant.
04 - Stir in sliced carrots, parsnips, potato chunks, and celery. Cook for 3 to 4 minutes, stirring occasionally, until vegetables begin to soften slightly.
05 - Return beef and any accumulated juices to the pot. Add rinsed barley, bay leaves, thyme, and beef broth. Increase heat to high and bring to a boil.
06 - Reduce heat to low, cover tightly, and simmer for 1½ hours. Stir occasionally to prevent sticking and ensure even cooking.
07 - Remove the lid and continue simmering uncovered for 30 minutes. The stew will thicken naturally as the barley releases starch and the liquid reduces.
08 - Remove and discard bay leaves. Stir in chopped parsley. Taste and adjust seasoning with additional salt and pepper as needed.
09 - Ladle hot stew into bowls and garnish with additional fresh parsley. Serve immediately while steaming hot.