Pie Crust: In a food processor (or a bowl) combine flour, salt, and sugar. Pulse (or cut) butter into flour mixture. Continue to pulse a few more times until butter is in pea sized chunks. Pulse in ice water 1 tablespoon at a time until dough begins to come together. (Test your dough by pinching some together with your fingers. If it holds together, it is ready.) Remove from food processor (or bowl) onto a piece of plastic wrap. Form into a disc and wrap in plastic. Place in refrigerator to chill for one hour (or up to two days).
Apple Filling: Peel and dice apples into 1 inch cubes and place into a medium bowl. Add brown sugar, cinnamon, nutmeg, flour, and vanilla extract. Toss to coat. Cover and refrigerate for 30 minutes.
Preheat oven to 400 degrees and line a baking sheet with parchment paper. Set aside.
Remove dough from refrigerator and separate into 6 equal pieces. Roll each piece of dough into a rough circle, about ⅛" thick.
Remove apples from refrigerator and distribute filling between the 6 pie crusts. Fold dough up around apple filling and pinch together, leaving a 'window' on the top.
Egg Wash: Whisk together the egg and water. Gently brush egg wash over each galette to coat the crust. Sprinkle sugar over egg wash.
Bake for 30-35 minutes or until crust is golden brown. Remove and allow to cool for 5 minutes before transferring off baking sheet. May be served warm or room temperature.
Optionally: Serve with whipped cream or vanilla ice cream.
Store-bought pie crust can be used instead if desired.
Pie can be served warm or room temperature. Leftover pies should be stored at room temperature in a tightly sealed container. Pie will keep for 2-3 days, but pie crust will soften as it sets.