In a non-stick pan, heat some oil over medium heat.
Add the chicken pieces and cook until they are golden brown on all sides.
Chicken
Remove the chicken from the pan and set aside.
In the same pan, add the celery, onion, and leek. Cook until they are softened and fragrant.
Celery, Onion, Leek, Baby Onions, Bacon Lardons
Return the chicken to the pan and add thyme, bay leaves, and white wine.
Thyme, Bay Leaves, White Wine
Bring the mixture to a simmer and let it cook for a few minutes to allow the flavors to meld together.
Add chicken stock and tarragon to the pan and bring to a boil.
Chicken Stock, Tarragon
Reduce the heat to low and let it simmer for about 30 minutes, or until the chicken is cooked through and tender.
Remove the chicken from the pan and set aside.
Turn off the heat and let the sauce cool slightly.
Using a blender or immersion blender, puree the sauce until smooth and creamy.
Return the sauce to the pan and add the cooked chicken back in.
Stir in the cream, and let the sauce simmer for a few more minutes to thicken.
Season the sauce with salt and pepper to taste.