Step 1: Cook the wild rice. In a medium pot, combine wild rice blend with 3 cups of chicken broth. Bring to a boil, then reduce heat, cover, and simmer for 40-45 minutes, or until rice is tender and water is absorbed. Set aside.
Step 2: Sauté chicken and vegetables. In a large Dutch oven or pot, heat olive oil over medium-high heat. Add diced chicken and cook until lightly browned and cooked through, about 5-7 minutes. Remove chicken from the pot and set aside.
Step 3: Cook aromatics. Add chopped onion, carrots, celery, and optional mushrooms to the same pot. Cook, stirring occasionally, until vegetables are tender, about 8-10 minutes.
Step 4: Make the roux. Push vegetables to one side of the pot. Add butter to the empty side and let it melt. Sprinkle flour over the melted butter and whisk continuously for 1-2 minutes to create a roux.
Step 5: Build the soup base. Gradually whisk in the remaining 3 cups of chicken broth into the roux, stirring until smooth and lump-free. Bring to a gentle simmer, stirring frequently, until the soup thickens, about 5-7 minutes.
Step 6: Combine and simmer. Stir in the cooked chicken, cooked wild rice, dried thyme, dried sage, pepper, and salt. Reduce heat to low, cover, and simmer for 15-20 minutes, allowing flavors to meld.
Step 7: Finish with cream. Stir in the heavy cream and heat through gently for 2-3 minutes, being careful not to boil. Taste and adjust seasonings as needed.
Step 8: Serve. Ladle the hot soup into bowls and garnish with fresh chopped parsley. Serve immediately with crusty bread.