Make the celery soup by adding two tablespoons of butter to a heavy-bottomed pot over medium heat.
Add the 5 cups of celery, leek, and onion to the pot. Cook, stirring occasionally, for 10 minutes.
Add the garlic and cook, stirring constantly, for 1 minute.
Add the chicken broth and bay leaves.
Bring to a boil then reduce heat to low and simmer until the veggies are very tender, about 30 minutes.
Braise the remaining celery while the soup is simmering, by heating the last tablespoon of butter in a small skillet over medium heat.
Add the finely diced celery and cook, stirring often, for 1 minute.
Add 1/2 cup of the soup liquid to the pan to allow the celery to braise while the soup is simmering. Reduce the heat to simmer.
Blend the soup when the veggies are very tender.
Remove the bay leaves from the soup and blend in batches with a very high-powered blender until creamy and smooth.
Add the cream to the soup and taste.
Season with sea salt and freshly cracked pepper to taste.
Add the braised celery and stir to combine.
Ladle into bowls and serve immediately. Enjoy.