For Crust: in a food processor combine the first 4 ingredents and pulse to combine. Add egg yolk and 1 Tbls of water. Pulse until starts to form a ball. If mixture is too wet or too dry add flour or water to get the right consistency.
Turn out onto a floured surface and knead a few times. Form into a disk, wrap in plastic wrap and refridgerate until ready to use.
When ready to use remove from fridge about 20 minutes to allow to warm up.
To make the filling:.
Coat bottom of stock pot with olive oil and put over medium heat.
Add onions, celery, and carrtos.
Sprinkle with salt and saute for 7 to 8 minutes.
Add garlic and sweat for 2 to 3 more minutes.
add Chicken and Chicken stock.
Stock should cover chicken if not then add enough water to cover chicken.
Bring to boil and then simmer for 30 minutes.
While chicken is simmering: coat squash with oil and salt and roast in over at 350 for about 15 minutes until cooked.
When chicken is cooked, remove it and the veggies from the stock.
Remove meat from bones and stir in bowl withy veggies. add squash.
Add salt if needed.
Stir in green beans and sage.
Melt 4 Tbls butter in saucepan.
Add flour and stir to combine. Cook for 6 to 7 minutes.
whisk in the stock made when the chicken boiled.
Bring to a boil and simmer until has a gravy like consistency - about 20 minutes.
Preheat oven to 375.
Put chicken mixture into a 2 quart casserole idsh and ladle gravy over until dish is 3/4 filled.
Dust work surface with flour and roll out dough to the shape of the casserole. Drape over dish and press edges around edge of dish.
Cut a couple of vents in top and brush with egg wash.