Mix the flour, salt, and baking powder together in a large bowl. Add the butter/margarine and use your hands to crumble the fat into the flour until it becomes crumbly.
Add the water, a little at a time until a slightly stiff but workable dough is formed.
Knead the dough for about a minute or even less, the lesser the better.
Cover it up with plastic wrap and place it in the fridge to chill for about 20 minutes. (skip this step if you don't want a super flaky pie).
Roll out the pastry dough to your desired thickness on a lightly floured work surface.
use a knife to cut into rectangles or circle of your desired size.
Fill the cut-out pastry with the chicken pie filling, but don't overfill so that you will be able to close the pie easily.
Crack and whisk one large egg inside a bowl and brush the edges of the pie pastry with the egg then, fold the dough over to close it up and crimp the edges with a fork.
Use the remaining whisked ggg to brush the surface of the Chicken Pie.
Use a fork to prick the surface of the pie about two or three times and place the pies in a parchment-lined baking sheet.
Bake in a 350°F preheated oven for 20 to 25 minutes or until golden brown. Enjoy!