Melt 2 tablespoons of butter in a large 6-quart Dutch oven or heavy soup pot over medium heat. Add the diced onion, carrots, and celery; cook for 5 to 6 minutes until softened.

Add remaining 2 tablespoons butter and sliced mushrooms; sauté for 4 minutes until mushrooms are tender and lightly browned. Stir in minced garlic and fresh thyme, cooking for 1 minute until fragrant.

Sprinkle the flour over the vegetables. Cook, stirring constantly for 2 minutes, to cook out the raw flour taste and create a roux base.

Slowly pour in the chicken bone broth while whisking constantly to ensure no lumps form. Stir in rinsed wild rice blend, poultry seasoning, salt, pepper, and bay leaves.

Submerge whole chicken breasts into the liquid. Bring the soup to a boil, then reduce heat to low, cover with a tight-fitting lid, and simmer gently for 25 to 30 minutes.

Remove chicken breasts with tongs and place on a cutting board. Shred the chicken into bite-sized pieces with two forks.

Check the wild rice; if it needs a few more minutes to become tender and crack open, continue simmering uncovered for 5 to 10 minutes.

Return shredded chicken to the pot. Stir in the heavy cream and let simmer gently for 5 minutes until soup is rich, creamy, and thoroughly heated through (do not boil hard once cream is added).

Discard bay leaves. Taste and adjust seasoning with additional kosher salt and cracked black pepper as desired.

Ladle steaming soup into warm ceramic bowls, garnish with fresh thyme leaves, and serve with warm crusty bread.