To make the pie dough: Combine the flour, sugar and salt in the bowl of a stand mixer fitted with the paddle attachment. Beat on low just to combine. Add the butter and beat on low speed to cut it into the dry ingredients - the pieces of butter should be no bigger than small peas when you're finished. Add the water to the mixer and mix on low just until the dough starts to come together and there are no more dry bits in the bowl. Turn out onto your work surface and shape the dough into a ball. Divide in half, shape each half into a disc and wrap in plastic wrap. Refrigerate for at least an hour or up to 2 days.
Preheat oven to 350 F. Line two baking sheets with parchment paper.
Remove one disc of dough from the fridge. On a lightly floured work surface, roll the dough out until it is about 1/8 to 1/4-inch thick (the shape doesn't matter). Use a 2 1/2-inch round cookie cutter to cut as many rounds as possible from the dough. Transfer them to the prepared baking sheets and pop in the refrigerator while you repeat the process with the second disc of dough. Refrigerate all of the rounds until you finish prepping the apples.
Peel the apples. Starting from one outside edge, cut thin (1/8 to 1/4-inch) slices from the apple until you reach the core in the center. Repeat starting on the opposite outside edge. Using a 1 3/4-inch round cookie cutter, cut small discs from the apple slices. Add the apple discs to a bowl and top with the lemon juice, tossing to coat (this stops them from browning as quickly). In a small bowl, stir together the sugar, cinnamon and nutmeg.
To assemble the cookies: Brush one side of a round of dough with water (this helps seal the cookies). Grab one apple disc, and coat it in the cinnamon-sugar mixture. Place it on the dough round and top with a second round of dough. Press the edges to seal, then use a fork to crimp the edges. Repeat using the remaining dough rounds and apple discs.
Make egg wash by beating the egg with 1 teaspoon of water. Brush each of your apple pie cookies with the egg wash, then sprinkle them with the sanding sugar, if you're using it. Use a paring knife to cut slits in the tops of the cookies.
Bake for 25-30 minutes, or until the cookies are puffed and golden brown. Transfer the baking sheets to wire racks to allow the cookies to cool (that said, these are great warm so feel free to dig in as soon as they're cool enough that you won't burn your mouth!).
by The Savvy Kitchen