Chicken Casserole with Mustard & Tarragon

I made this hearty dish twice in the month of December. It is really satisfying on snowy days!

1/4 cup cup extra-virgin olive oil
4# chicken, cut into pieces (I cut each chicken breast into halves)
1 onion, finely chopped
1 leek, sliced
1 clove garlic, finely chopped
11 oz mushrooms, sliced
1 Tb chopped tarragon or 1/2 tsp dried (I have also used sage in place of tarragon)
1 1/2 cups chicken stock
3/4 cup whipping cream
2 tsp lemon juice
2 tsp Dijon mustard

Preheat oven to 350 degrees. Heat 2 Tb of olive oil in a flameproof casserole dish over medium heat, and cook chicken in batches until golden. Remove from dish.

Add the remaining oil to the casserole and cook the onion, leek, and garlic over medium heat for 5 minutes or until soft. Add the mushrooms and cook 5-7 minutes or until they are soft and browned. Add the tarragon, chicken stock, cream, lemon juice, and mustard, bring to a boil, and cook for 2 minutes. Return the chicken to the casserole dish and season well. Cover.

Place the casserole dish in the oven and cook for 1 hour or until the sauce has reduced and thickened. Season to taste and serve over rice or with potatoes.

Serves 4-6.