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

In a large Dutch oven or pot, heat olive oil over medium heat. Add the onion, carrots, and celery. Cook for 5 to 7 minutes, stirring occasionally, until softened and the onion turns translucent.

Add the sliced cremini mushrooms and cook for another 5 to 7 minutes until they release their moisture and begin to brown lightly at the edges.

Stir in the minced garlic, dried thyme, dried sage, dried rosemary, and red pepper flakes if using. Cook for about 1 minute, stirring constantly, until fragrant. Do not let the garlic burn.

Pour in the remaining 4 cups of chicken broth. Add the cooked wild rice and shredded chicken. Bring to a simmer over medium heat, then reduce to low, cover, and cook for at least 30 minutes, stirring occasionally.

Stir in the heavy cream and dry sherry if using. Add the fresh parsley and season generously with salt and pepper. Heat gently but do not bring to a boil after adding the cream to prevent curdling.

Ladle the Autumn Wild Rice Soup into bowls and top with toasted pecans and Parmesan cheese if using. Serve immediately.