In a medium saucepan, combine the rinsed wild rice with 4 cups of the chicken broth. Bring to a boil over high heat. Reduce heat to low, cover, and simmer for 45-50 minutes, or until the rice is tender and the grains have split open. Check periodically and add more broth if needed. Drain any excess liquid and set aside.

In a large pot or Dutch oven, heat the olive oil over medium heat. Add the chopped onion, carrots, and celery. Cook, stirring occasionally, for 5-7 minutes, or until softened and the onion is translucent. Add the sliced cremini mushrooms and cook for another 5-7 minutes, or until tender and have released their moisture. Add the minced garlic, dried thyme, dried sage, dried rosemary, and red pepper flakes (if using). Cook, stirring constantly, for about 1 minute, or until fragrant.

Pour the remaining 4 cups of chicken broth into the pot with the sautéed vegetables. Add the cooked wild rice and shredded cooked chicken. Bring to a simmer over medium heat. Reduce heat to low, cover, and simmer for at least 30 minutes, or up to an hour, stirring occasionally.

Stir in the heavy cream (or coconut milk) and dry sherry (if using). Add the chopped fresh parsley. Season with salt and pepper to taste. Heat through gently, being careful not to boil the soup after adding the cream.

Ladle the Autumn Wild Rice Soup into bowls. Garnish with toasted pecans or walnuts and grated Parmesan cheese (if using). Serve immediately.