Chicken Pot Pie

1 rotisserie chicken
2 Tablespoons extra virgin olive oil
1/4 pound button mushrooms, chopped
2 carrots, chopped
3 ribs celery, chopped
Salt and ground black pepper
3 Tablespoons butter
3 Tablespoons flour
1/2 cup white wine
1 cup milk
1 1/2 cups chicken stock
5-6 sprigs fresh tarragon leaves, chopped
3 tablespoons Dijon mustard
1 cup frozen peas
1 sheet puff pastry or pie dough, defrosted if frozen

Preheat oven to 375 degrees F. Sauté the onion, mushrooms, carrots, and celery in olive oil, season with salt and pepper, and cover. Cook, stirring occasionally, until softened, 7-8 minutes. While the veggies are cooking, pull the chicken off the bones and shred.

In another pan, melt butter, add the flour and cook for about a minute. Whisk in white wine, milk, chicken stock. Bring up to a simmer then add the tarragon, Dijon, veggies, peas and shredded chicken. Bring back up to a simmer, season with salt and pepper, and cook until the sauce has thickened, 2-3 minutes.

Transfer to a casserole dish and cover with the pastry dough, trimming it as needed to cover the entire surface. (You can also do it in little individual size dishes.) Make a few slits in the dough to allow steam to escape, then brush the top with the beaten egg (optional).

Bake the pot pie until the filling is bubbling and the crust is golden brown, about 30 minutes. Serve warm.