Heat the olive oil in a heavy-based pan over medium-high heat. Add the pancetta and fry for 5 minutes until golden. Add the leek and garlic and cook for 2 minutes until softened.
Meanwhile, toss the chicken thighs in the seasoned flour and shake off any excess. Add to the pan and brown for 2-3 minutes, then stir through the mushrooms and potatoes. Pour over the wine and cook for 1 minute on a high heat to reduce, then add the stock, double cream and bay leaves. Season to taste.
Turn down the heat to a simmer. Cover and cook for 20 minutes until the potatoes are soft and the chicken is cooked through. Stir through the tarragon to serve.
* Wash your hands after handling raw meat.
Chef's tip: this will make a fantastic filling for a hearty chicken pie.