Whisk the flour, sugar and salt together in a large bowl. Use a pastry knife or a fork to cut the shortening into the flour mixture. The shortening should be pea sized when done.
Mix the milk and water together in a measuring cup. Pour a bit at a time into the flour mixture, until the dough comes together. You may not need to use all of it.
Cut the dough into 2 pieces and flatten each one. Wrap each disc in plastic wrap and store in the refrigerator while you make the cherry pie filling.
To make the cherry pie filling, combine the sugar, corn starch, lemon juice, and salt in a large saucepan. Mix until cornstarch has dissolved, then add cherries. The cherries will slowly release their juices. Bring to a boil and stir constantly until thickened. Remove from heat and add in kirsch. Stir to combine and set aside.
Preheat the oven to 400°F and grease a 9-inch pie dish. Remove one of the pie dough discs to a floured worksurface. Start in the middle of the disc and roll out up and down. Turn the dough a quarter turn with your hands and roll out up and down. Continue with the rolling and turning until you have a 12 inch diameter circle. Carefully place it into the prepared pie dish, using your fingers to smooth it out. Trim off any extra overhang with a knife.
Fill the pie crust with the filling and dot the top with butter pieces. Roll out the second dough disc on a floured work surface until you have a 12-inch diameter circle.
Use a pastry wheel or a knife and cut strips out of the dough, about 1 inch wide. Thread the strips over and under one another. Use milk to seal the edges of the strips onto the pie crust edges. Crimp or flute the edges of the pie crust. Brush the top of the pie with an egg wash and sprinkle sugar over top.
Place the pie onto a large baking sheet and bake for 20 minutes at 400°F and then turn the oven down to 375°F and bake for another 30-40 minutes. Remove the pie from the oven and let it cool on a wire rack for 2-3 hours so the filling sets up.
Store the cherry pie in the refrigerator covered for up to 3 days.