In a large Dutch oven over medium heat, melt butter.
Add onions, carrots, celery, leeks and garlic.
Sauté about 5-7 minutes until veggies are tender.
Add rinsed and well-drained artichoke hearts.
Stir in gluten-free flour.
Slowly add chicken broth about ¼ cup at a time.
Add half-and-half and then heavy whipping cream, whisking while each addition is incorporated.
Add salt, pepper and red pepper flakes and cook on low heat until mixture thickens—about 5-10 minutes.
Add cheese and stir until cheese is melted.
Ladle soup into bowls.
Garnish with additional cheddar cheese, if desired.