Cook the ground beef in a large stock pot over medium heat, breaking it up into smaller chunks, until the meat is no longer pink. With a slotted spoon, remove the ground beef from the pot and set aside. Drain the grease and return the pot to the burner.
Melt the butter with the oil. Gradually whisk in the flour, forming a roux. Stirring constantly, cook the roux for approximately six minutes until it turns light brown, similar to the color of peanut butter.
Add the onion, celery and bell pepper. Cook for five minutes until the vegetables are soft.
Add the garlic and cook for 30 seconds.
Add the tomato sauce, crushed tomatoes, beef broth, bay leaves, thyme and Worcestershire sauce. Bring the soup to a boil, then cover, reduce the heat to low, and cook for one hour, stirring every 15 minutes.
Remove and discard the bay leaves.
Add the hardboiled eggs, lemon juice, sherry, parsley and cooked hamburger. Stir to heat through. Serve hot.