Begin by seasoning the pre-cooked rotisserie chicken with kosher salt and freshly ground black pepper to enhance its flavor. Shred the chicken into bite-sized pieces. Set aside while you gather and prepare the remaining ingredients.

In a large stockpot, heat 2 tablespoons of olive oil over medium heat. Once the oil glistens, add the shredded rotisserie chicken and sauté it for 2-3 minutes until warmed through.

Add 2 tablespoons of unsalted butter to the stockpot, letting it melt completely. Stir in sliced cremini mushrooms, diced onion, chopped carrots, and minced celery. Sauté these vegetables for about 3-4 minutes until tender and fragrant.

Next, add 2 cloves of minced garlic and 1 teaspoon of dried thyme to the pot. Stir continuously for 1 minute until the garlic becomes slightly golden and fragrant.

Sprinkle in 1/4 cup of all-purpose flour, whisking constantly to create a roux. Cook for about 1 minute until the mixture is golden and well combined.

Slowly pour in 4 cups of chicken stock, whisking to combine. Add in the bay leaf and the previously sautéed chicken. Bring the mixture to a gentle simmer for 4-5 minutes.

Reduce the heat to low and stir in 1 cup of half and half. Heat through for an additional 2-3 minutes without boiling, adjusting seasoning with extra salt and pepper as needed.

Ladle the soup into bowls, removing the bay leaf before serving. Garnish each bowl with freshly chopped parsley.