Heat olive oil in a large stockpot or Dutch oven over medium heat. Season chicken thighs with salt and pepper, to taste. Add chicken to the stockpot and cook until golden, about 2-3 minutes; set aside.

Melt butter in the stockpot or Dutch oven over medium heat. Add garlic, mushrooms, onion, carrots and celery. Cook, stirring occasionally, until tender, about 3-4 minutes. Stir in thyme until fragrant, about 1 minute.

Whisk in flour until lightly browned, about 1 minute. Whisk in chicken stock, bay leaf and chicken thighs, and cook, whisking constantly, until slightly thickened, about 4-5 minutes.

Stir in half and half until heated through, about 1-2 minutes; season with salt and pepper, to taste. If the soup is too thick, add more half and half as needed until desired consistency is reached.

Serve immediately, garnished with parsley and rosemary, if desired. Notes

*Half and half is equal parts of whole milk and cream. For 1 cup half and half, you can substitute 3/4 cup whole milk + 1/4 cup heavy cream or 2/3 cup skim or low-fat milk + 1/3 cup heavy cream.