Start by heating up the butter or ghee over medium heat.
Add onions and saute until they are tender.
With a whisk, blend in the flour and celery salt. Gradually add the turkey stock and milk.
Whisk constantly until the sauce is thick.
Put the turkey in a small bowl and add ½ c of the sauce and mix well.
Roll out the pastry into a rectangle and cut into 8 pieces.
Divide the turkey mixture evenly between the pastry pieces. Using a pastry brush, put a line of the egg wash around all of the edges of the pastry pieces.
Fold the pastry over and crimp the edges with a fork to seal the turkey inside.
Poke a few holes in the top of each turnover to let the steam escape.
Now use the rest of the egg wash on the tops of the turnovers.
Transfer the turkey turnovers to a lightly greased baking sheet.
Bake in a preheated 425°F oven for 25 minutes or until golden brown.
Notes
When you are ready to serve the turnovers, reheat the rest of the sauce and add more milk to bring it to the proper thickness for gravy.