In a food processor, blitz All-Purpose Flour (2 1/4 cup), Corn Starch (1/4 cup), Baking Powder (1/4 teaspoon), Caster Sugar (2 tablespoon), Salt (1/4 teaspoon) and Salted Butter (1 cup) to breadcrumb consistency.
Drizzle in Egg (1), Water (2 tablespoon), and Distilled White Vinegar (1/4 teaspoon). Continue to blitz until the mixture turns from white to yellowish crumbs. If the dough can be pitched into a dough, transfer onto a kneading surface. Else, add more water and blitz.
Press the crumbs together to form into one dough. Divide the dough into two and form each into a round disk.
Wrap them individually with plastic wrap and put it in the fridge for at least an hour.
Meanwhile, melt Salted Butter (2 tablespoon) a medium heat pan and throw in Apple (800 gram).
Add in Caster Sugar (1/2 cup), Ground Cinnamon (1/4 teaspoon) and Lemon (1/2).
Mix well and cover with a lid. Bring it to a boil and simmer for 3 to 4 minutes.
Turn the heat down to low. Combine Water (2 tablespoon) and Corn Starch (1 tablespoon) and drizzle it in. Cook until the sauce is well thickened. Turn off the heat and let it cool.
Take one of your chilled dough and roll it out between two parchment paper. Make sure to roll out about an inch larger than the tart pan itself. Let it chill in the fridge for 10 minutes to firm up before pressing it into the tart pan.
Once you have pressed it evenly, transfer the cooled filling into the shell and put it in the fridge to chill while you roll out your second dough.
Roll out your second dough that has been chilled and use your favorite cookie cutter to cut out shapes for the top crust.
Trim around the edges to make sure that it is even. Beat the Egg (1) to make an egg wash and apply the egg wash to your top crust.
Finally, chill your pie while preheating the oven to 410 degrees F (210 degrees C). You would want the butter in the crust to firm up hard before putting into the oven.
Bake for 15 minutes.
Lower temperature down to 350 degrees F (180 degrees C) and bake it for another 45 minutes.
Let it cool for an about an hour or two.
Serve warm. Enjoy!