Saute onion and celery and butter over medium heat until onion is translucent.
Lower heat to medium low and slowly add flour, 1/4 cup at a time. Whisk constantly until mixture is smooth.
Slowly add chicken broth, increase heat slightly and stir constantly until thickened.
Add carrots and broccoli and simmer on low to medium low heat for 10 minutes, stirring often. Soup should be barely bubbly.
Add cream and mix well. Take care to stir constantly and that the soup does not get too hot.
Slowly add cheese, one cup at a time, mixing well after each addition.
When the cheese is melted and the soup is smooth add the salt, pepper,crushed red pepper, paprika and dijon mustard. Allow to simmer on very low heat for 5 to 10 minutes to allow flavors to blend.
Enjoy!