2) Preheat oven to 210C/Gas Mark 7.
3) Meanwhile, in a large skillet melt butter over medium-high heat. Add chicken, pepper, and shallots and cook 5 minutes, stirring frequently. Stir in flour, salt, tarragon, and black pepper. Add milk and cream all at once. Cook and stir until thickened and bubbly. Stir in wine, peas, carrots and potatoes; heat thoroughly.
4) Transfer the hot chicken mixture to a 1.5L casserole. Place pastry over the hot chicken mixture in casserole dish. Brush puff pastry with egg wash then cut slits in the pastry to allow steam to escape. Bake in the preheated oven for 30 to 45 minutes.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.