Melt 2 tablespoons of butter in a large pot or Dutch oven over medium heat. Add the onion, carrots, and celery. Sauté for about 5 to 7 minutes until the vegetables are soft.

Add the minced garlic and cook for 1 minute until fragrant.

Stir in the chicken pieces, wild rice, chicken broth, thyme, rosemary, salt, and pepper. Bring the mixture to a boil.

Reduce the heat to low, cover the pot, and let it simmer for 40 to 45 minutes. The rice should be tender and the chicken cooked through.

In a small saucepan, melt the remaining 2 tablespoons of butter over medium heat. Whisk in the flour and cook for 1 minute to create a roux.

Slowly whisk the heavy cream into the roux until smooth and thickened.

Pour the cream mixture into the large soup pot. Stir well to combine everything.

If using spinach, stir it in now and let it wilt for 2 minutes.

Taste the soup and add more salt or pepper if needed. Serve hot.