Step 1
Heat butter in a large ovenproof pot over medium heat. Add onion, garlic, rosemary, red pepper flakes, thyme, paprika, salt, and black pepper. Cook and stir until onion is translucent, 5 to 7 minutes. Whisk in 3/4 cup flour, creating a paste; stir until paste begins to bubble, about 1 minute more. Add broth and milk; increase heat to medium-high. Bring to a rolling boil, stirring constantly, about 2 minutes. Continue stirring until sauce thickens, about 2 minutes more. Reduce heat to medium-low. Add turkey, carrots, celery, and potatoes. Cover soup and simmer for 20 minutes.