Put the chopped cauliflower into a microwave safe bowl with a little water and salt. Cook until the cauliflower is soft, but not mushy.
Meanwhile, melt the butter in a large saucepan. Add the onion and carrots and cook until soft. Season with salt, pepper, and the red pepper flakes.
Add the flour and stir for a minute or two.
Slowly add the chicken broth and mix well. Add the half 'n half and cheese and cook until warm and the cheese is melted.
Add the cauliflower to the pan and simmer for several minutes. Test the seasoning and adjust if necessary.
With an immersion blender, (**see note) blend the soup until smooth and creamy.
Add the parsley and serve.
Top with additional cheese, chives and croutons if desired.
* I used all half 'n half. The soup was very rich and creamy. You could easily add more chicken broth or use whole milk. Or, using any combination of chicken broth, milk, and half 'n half.** I used an immersion blender right in the sauce pan. If you use a regular blender, remember to do small batches at a time and be careful not to burn yourself! :)