11tablespooncold unsalted butter 160 grams or 5-1/2 oz.
1large egg yolk
For the filling:
4cupsapplespeeled and thinly sliced
1large egg whitebeaten well
To make the dough:
In the bowl of your stand mixer fitted with the paddle, on low-speed, mix the flours with the sugar and salt.
Add in the cubed butter, and blend the flour with the butter for a couple of minutes until just small pieces of butter are visible and the flour sticks together when you hold it in your hand.
In a separate small bowl, whisk the egg yolk with the milk and add it to the flour mixture all at once while mixing on low-speed for about 15-20 seconds, or until the dough comes together.
If you want to make two smaller galettes, divide the dough in half and wrap each half with plastic wrap.
Let the dough rest in the refrigerator while you prepare the filling.
To make the filling:
In a medium sized bowl, combine the apples with the sugar, cinnamon, nutmeg, lemon juice, flour and salt. Mix well so that the apples slices are well coated with the sugar and spice.
To make the galettes:
Place a rack in the centre of your oven and preheat oven to 350ºF.
Line a baking sheet with parchment paper.
Take the dough out of the refrigerator and let it sit at room temperature for a few minutes. Flour your surface and roll out each half of dough (or just one, if you are making one large tart) into a disk that is just about 1/4″ thick.
Transfer the dough onto the lined baking sheet and top the centre of each dough disk with the apple slices.
Gather the dough around the apples by overlapping the creases of dough over each other slightly.
Whisk the remaining egg white (from the egg used in the dough) and brush the dough with it.
Sprinkle the top of the galettes with the turbinado sugar.
Bake the galettes on the baking sheet for 40 to 45 minutes or until the pastry is golden brown.
Let the galettes cool for 20 minutes before serving warm, or you can let it cool completely and serve it at room temperature.
You can make the dough the day before. Just make sure to remove it from the refrigerator and let it sit for approximately 20 minutes (or until it's pliable) at room temperature before rolling it out.