Preheat oven to 375°F and line cookie sheet with parchment paper.
Thinly slice 2 peaches, place in a bowl and toss with the next 5 ingredients. Set aside.
Using 1/2 of the Boiling Water pastry recipe, roll out the ball on the counter between two sheets of plastic wrap until you have a disc about 11” round and the dough is thin. Transfer to the cookie sheet. Spoon the filling into the centre of the pastry leaving about a 2” border around it. You will have excess juice in the bowl. Put a couple teaspoons of the excess juice on top of the filling, being careful not to make it too runny.
Using the sides of the parchment paper, fold the ends of the pastry into the centre and pinch to enclose the peaches.
Lightly beat the egg with a splash of milk and brush onto the crust, (you will not use all the egg.) Sprinkle with sugar.
Bake in the centre of the oven for 35 – 40 minutes or until the crust is golden brown and the filling is bubbly. Cool on cookie sheet for 10 minutes then slide off with the parchment paper to a cooling rack to cool completely. This will allow the filling to set up. Store in fridge, serve cold or reheated.
Pour boiling water over shortening and stir until blended.
In a separate bowl, combine flour, baking powder and salt. Add all at once to liquid mixture and mix until blended. You can use your hands but do not over-mix or pastry will be tough. Form pastry into a ball.
Wrap with plastic wrap and chill in fridge for at least one hour. Can be stored overnight.
Roll out and cut chilled pastry to desired size.