Cook bacon in a large saucepan over medium heat until crisp. Remove with a slotted spoon and set aside.
Add onion, garlic, and celery to the bacon fat and cook 3-4 minutes or until onion softens slightly.
Stir in chicken broth, potatoes, and thyme. Bring to a boil, reduce heat to a simmer and cook covered 10 minutes or until potatoes are tender. Stir in cream and simmer for 5 minutes longer.
Combine cornstarch and 1 tablespoon of water to create a slurry. Whisk into the simmering soup and simmer 1 minute. Stir in half of the bacon. Season with salt, pepper, and cayenne to taste.
Spoon into bowls, top with parmesan cheese, remaining bacon and green onions.
