Preheat the oven to 325°F (163°C).
Pat the chicken pieces dry with paper towels.
In a small bowl, combine 2 teaspoons of salt and ½ teaspoon of black pepper. Rub the seasoning over and under the skin of the chicken.
In a 3–5 quart Dutch oven, melt the butter over medium-high heat.
Add the chicken and brown on both sides, about 3–5 minutes per side. Remove and set aside.
Add the mushrooms, shallots, celery, and garlic to the pot. Cook, stirring occasionally, until softened.
Season with the remaining salt, pepper, sage, and parsley.
Once the mushrooms are tender and the shallots are translucent, sprinkle the flour over the vegetables and stir well to coat.
Pour in the additional ½ cup chicken stock, scraping up any browned bits from the bottom of the pot.
Gradually add the remaining 2 cups chicken stock, about 1 cup at a time, stirring continuously.
Bring to a gentle simmer and cook for about 5 minutes, until the sauce thickens slightly.
Stir in the potatoes.
Return the browned chicken pieces to the pot, placing them on top of the vegetables and potatoes.
Transfer the Dutch oven to the preheated oven.
Roast for 40–45 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
Remove from the oven and stir the cream into the sauce.
Cover with a lid or tent with foil and let rest for at least 10 minutes.
Serve hot with the creamy herb sauce spooned over the chicken, potatoes, and mushrooms.