Sift together flour, baking powder, and salt in a large bowl.

In a separate container, combine shortening and hot water. Stir until the shortening melts.

Add the egg yolk to the liquid mixture and blend well.

Pour the liquid mixture into the flour mixture.

Mix until the dough comes together.

Form the dough into a disc.

Wrap the dough in plastic wrap and chill in the refrigerator for at least 2 hours, or preferably overnight.

Preheat oven to 425°F (220°C).

Divide the dough, reserving about 1/4 for the top crust.

On a lightly floured surface, roll out the larger piece of dough to fit the bottom of a 2-quart (8-inch) casserole dish.

Gently transfer the dough to the casserole dish, pressing it firmly against the bottom and sides.

Fill the crust with your desired pre-cooked meat casserole filling.

Roll out the remaining dough for the top crust.

Carefully place the top crust over the filling, removing any excess dough.

Cut 3-4 small slits in the top crust to allow steam to escape.

Seal the edges of the crust to the casserole dish with a fork or your fingers.

Brush the top crust with an egg wash for a golden-brown color.

Bake in the preheated oven for 25 minutes, or until the crust is golden brown and the filling is heated through.