In a large saucepan over medium heat, melt the butter until frothy. Add the celery and onion and sauté until vegetables are tender, about 4 minutes. Season with salt and pepper.
Whisk in the tomato paste until well combined, and then add the broth, Buffalo sauce, and cauliflower florets. Bring to a boil and then reduce heat to a simmer. Cook until the cauliflower is tender, about 5 to 10 minutes.
Transfer the soup to a blender and add the cream cheese. Blend until smooth, then return to the pot.
Stir in the cream and bring back to just a simmer, then stir in the chopped chicken. Divide among 6 bowls and garnish with chopped celery and bleu cheese.
Notes
Storage Information: Store the soup in the fridge in a covered container for up to 5 days. You can also freeze it for several months. Dairy-Free Option: Replace the butter with olive oil, then use dairy-free cream cheese and coconut cream.