Melt the butter in a large pot over medium heat, then add the carrots and celery and cook for 4 to 5 minutes until softened.
Stir in the flour, garlic powder, and thyme, cooking for 1 minute until the mixture forms a light roux.
Pour in the chicken broth while whisking constantly, then add the diced chicken and bring to a gentle simmer for 8 to 10 minutes until the chicken reaches 165°F / 74°C.
Add the gnocchi and cook for 3 to 4 minutes until they float and become tender.
Stir in the heavy cream and spinach, cooking for 2 minutes until the spinach wilts and the soup is creamy.
Ladle the soup into bowls and serve immediately while hot and creamy.