Heat olive oil in a large saucepan or dutch oven over medium heat. Add the stew meat, salt and pepper. Brown the meat, stirring occasionally (several minutes). If there is an excessive amount of grease, drain some of it out of the pan.
Return the pan to medium heat, add onion, worcestershire sauce and tomato paste. Stir with a wooden spoon, scraping the bottom of the pan to remove any brown bits. Add thyme, bay leaf and 3 cups of beef broth (this should be enough to cover the meat and onions. If not, add water until the meat is covered. Bring to a boil, then reduce heat and simmer covered for about 2 hours.
Once the meat is tender - but not falling apart, add the potatoes, celery, carrots and butternut squash. Pour over another 2 cups of beef broth and enough water to cover the vegetables. Raise heat and bring to a boil, then reduce heat and simmer partially covered for about 30 minutes - until the vegetables are tender.
If you’d like the broth thicker: In a bowl, whisk ¼ cup of flour with 1 cup water until smooth. Add the mixture to the stew,stirring until combined. This will thicken the sauce, and create more of a "gravy" consistency.
Add peas, and simmer the stew for another 5 minutes or so, until the sauce has thickened and the peas are cooked through. Add salt and pepper to taste (this will depend on how salty your beef broth is).
To serve: sprinkle each serving with minced parsley and/or thyme and serve with crusty bread on the side for dipping.