Elegant Chicken Pot Pie with Sweet Potato

2-3 boneless chicken breasts
1 cup dry white wine1 celery stalk, chopped, reserving leaves4-5 sprigs fresh thyme1 cup carrots, chopped1 large sweet potato, cubed into 1/2 inch cubes1 cup peas (frozen)butter1 package mushrooms (button or similar), sliced2 Tbsp flour1/2 cup creamsaltpepper
For the pastry1 cup flour4 Tbsp butter 1/4 cup cold water
Prep- preheat oven to 400 degrees- butter a casserole dish or large, deep pie dish. Alternatively, butter 6 deep ramekins or chili bowls- chop all vegetables, have flour, butter and cream ready (except butter for pastry, keep that cold!)
1) Combine the white wine and 1/2 of the thyme sprigs in a large saucepan. Bring to a simmer, add the chicken breasts & celery leaves, cover, and gently simmer until the chicken is just done.
2) Remove the chicken to a plate to cool. Remove the celery leaves and thyme and discard. Pour the remaining wine and juices into a bowl and reserve.
3) Using the same pan, melt 2 tbsp of butter. Add the celery, carrots, sweet potato, and remaining thyme sprigs. Saute at a medium-high heat until all the vegetables are just about soft. Do not stir too frequently, as you want the sweet potato to get a bit caramelized. Add the peas and continue cooking until all vegetables are soft.
4) Remove the thyme sprigs and discard. Remove the vegetables to a bowl and reserve.
5) Dice the chicken into 1/2 cubes.
6) Add 2 Tbsp butter to the same pan. When melted, add the mushrooms, and saute at a medium-high heat, stirring frequently, until the mushrooms have softened. Remove the mushrooms to the bowl with the other vegetables.
5) Using the same pan, add 2-3 Tbsp of butter. Heat at medium high until completely melted, but do not brown. Add 2 Tbsp of flour, stirring quickly with a whisk or spoon. The butter and flour mixture should begin to bubble. Turn the heat to medium and keep stirring until the roux turns a light brown. Slowly add the remaining wine the chicken had cooked in while stirring constantly. Remove from the head and add the cream slowly, again continuing to stir until smooth.
6) Add the vegetables and chicken to the sauce. Stir until everything is well coated. Pour into the casserole (or pie plate or ramekins).
7) Place the 1 cup of flour on the counter. Add the 4 Tbsp of butter, and cut the butter into the flour using a pastry knife. Alternatively, you can do this in a food processor. The butter/flour mixture should be the consistency of brown sugar.
8) Add cold water slowly, 1 Tbsp at a time, until the dough just holds together.
9) Roll the dough out into a sheet which will cover the casserole. Pastry dough can be made before hand and refrigerated before rolling out.
10) Place the dough over the casserole, directly on the chicken mixture. Brush the top of the pastry with some melted butter.
11) Bake for 20-30 minutes until the pastry is light brown, and the chicken mixture is bubbling.
12) Serve