Season and brown the beef: Toss beef cubes with flour, salt, and pepper. Heat vegetable oil in a large pot over medium-high. Brown beef in batches, then set aside.
Sauté the aromatics: In the same pot, cook chopped onion on medium heat until soft. Stir in garlic and cook another minute.
Combine the ingredients: Return beef to pot. Add carrots, potatoes, celery, tomatoes with juice, broth, Worcestershire, thyme, rosemary, and bay leaf. Stir well.
Simmer until tender: Bring to a gentle boil, then reduce to low and cover. Simmer 90 minutes to 2 hours, stirring occasionally. Add peas in the final 10 minutes.
Prepare the bread bowls: Cut tops off bread loaves and hollow them out, leaving a ½-inch shell. Brush insides with butter if desired and bake at 350°F (175°C) for 5–7 minutes.
Assemble and serve: Remove bay leaf. Ladle hot stew into bread bowls, garnish with parsley if desired, and serve immediately.