In a large bowl combine All-Purpose Flour (1 cup), Almond Flour (1/2 cup), Granulated Sugar (1/4 cup), and Salt (1/4 teaspoon). Cut the chunks of Unsalted Butter (1/2 cup) into the dry ingredients using a pastry cutter or a knife until the flour is crumbly with small bits of butter.
Drizzle Water (1/4 cup) and Apple Cider Vinegar (1 tablespoon) over flour mixture and toss with a fork until dough just starts to come together. Turn out onto a lightly floured surface and work gently to bring everything together and the dough has smoothed out.
Roll dough into a ball and then flatten into an approximate 6-inch disk. Cover with plastic wrap and chill for at least one hour.
Peel and core Granny Smith Apple (4) and then cut them into thin slices. Drizzle slices with the juice of the Lemon (1/2) as you slice to prevent oxidization.
To the apples add the Granulated Sugar (1/4 cup), All-Purpose Flour (1 tablespoon), Ground Cinnamon (1 1/2 teaspoon), and Ground Nutmeg (1 pinch). Toss to combine.
In a small bowl whisk together Egg (1) and Milk (1 tablespoon). This will be your egg wash.
Preheat oven to 375 degrees F (190 degrees C).
On a lightly floured surface, roll dough to an approximately 13-inch circle - adding a sprinkle of flour to the top and bottom as you go to prevent sticking.
Trim dough to a neat 12-inch circle by using a plate or pie plate as a guide or leave the edges uneven. Roll dough onto your rolling pin and transfer to a large parchment-lined baking tray.
Pile filling in the center and spread out towards the edge leaving a 1 1/2-inch border of plain dough. Fold the dough edge up and over the filling, crimping slightly as you go around.
Sprinkle the apples with dots of Unsalted Butter (2 tablespoon). Brush the pastry with egg wash and sprinkle with Coarse Sugar (to taste) if desired.
Bake in preheated oven for 40 minutes until the pastry is golden and apples are tender.
Remove from oven and allow to cool for at least 10 minutes before slicing into wedges and serving with ice cream.