Sear bones in oven safe heavy pot in oven or on stovetop for 5-10 minutes until sizzling. Pour boiling water over top to cover or almost cover bones. Add bay leaves and salt and simmer on stove top for at least 3 hours, up to 6 hours for best flavour. Add additional water if necessary during early stages of simmering to keep bones covered.
When broth has good beefy flavour, top up with some of carton of beef broth if necessary to keep liquid level even in pot. Save some for finishing soup.
Remove bones and pick off as much meat as possible when cool enough to handle.
Refrigerate broth overnight if possible to allow fat to solidify on top. Or make broth earlier in the day and finish later. Using a flat spatula, remove fat from top of broth and discard.
Return pot to stovetop and bring to a simmer. Finely dice onion, chop carrots and celery into similar sized pieces. Add to pot along with worcestershire sauce and simmer for 30 minutes.
Peel and dice potato. Add to pot and cook for 15 minutes or until vegetables are fork tender. Add more beef broth from carton if necessary.
Add green beans and simmer for 5 minutes, then add peas and heat only until broth comes back to a simmer. Remove from heat and serve immediately.
Garnish with reserved celery leaves and fresh cracked black pepper if desired.