Heat the olive oil in a large saucepan or saucepan over medium heat. Season the chicken thighs with salt and pepper to taste. Add chicken to skillet and cook until browned, about 2 to 3 minutes; put aside.
Melt the butter in the saucepan or pot over medium heat. Add garlic, mushrooms, onion, carrots and celery. Cook, stirring occasionally, until tender, about 3 to 4 minutes. Add thyme until fragrant, about 1 minute.
Add flour until lightly browned, about 1 minute. Add the chicken broth, bay leaf, and chicken thighs and cook, whisking constantly, until the mixture thickens slightly, about 4 to 5 minutes.
Stir in cream until heated through, about 1 to 2 minutes; Season with salt and pepper to taste. Serve immediately, garnished with parsley and rosemary, if desired.
