Make sure your pie crust is cold but not frozen, and is malleable enough to be rolled out.

Whisk together the crumble ingredients from flour to cinnamon, then use a fork or pastry blender to cut the cold butter into the mixture, until it resembles coarse crumbs. Place in fridge until ready to sprinkle over the galette.

Take the egg and separate the egg white out into a small bowl, lightly whisk with a fork, then set aside.

Place the remaining egg yolk in another small bowl, add a bit of tap water, lightly whisk with a fork, then set aside.

Squeeze the juice of a 1/2 lemon into a small bowl, then whisk in the cornstarch until combined. Set aside.

Peel, core, and slice your apples into thin pieces, then place them into a large bowl.

Melt 1 tbsp unsalted butter in a large skillet. Add apple slices and sauté for 8-10 minutes over medium heat, stirring often, until lightly softened.

Remove the skillet from the heat and add the lemon juice/cornstarch mixture, 5 tbsp brown sugar, 5 tbsp granulated sugar, 1 tsp cinnamon, 1/2 tsp nutmeg, and 1/8 tsp ground cloves. Stir to combine until apples are thoroughly coated with the spices, sugar, and cornstarch mixture. Set aside.

Preheat the oven to 375F.

Place a sheet of parchment paper on a baking sheet. Set aside.

Roll out your pie down on a lightly floured surface. The dough should be roughly 1/4 inch thick and formed into a roughly circular shape, but it doesn't have to be perfect. You're aiming for "rustic" here!

Move your dough onto the parchment-lined baking sheet, then gently brush the dough with egg white wash, edge to edge. Discard remaining egg white.

Use a slotted spoon the remove the apples from the skillet (leave the juice behind) and place the apples onto the center of the dough, spreading them out a bit over the crust but leaving a 1.5-2 inch border on all sides.

Gently fold the crust border up onto the fruit, so that the apples are encased within a frame of dough.

Brush the exposed crust lightly with egg yolk wash, then sprinkle with sanding or turbinado sugar.

Remove the crumble from the fridge and sprinkle it over the apple filling. (Note: you may not need to use all the crumble.)

Place galette into the oven on the baking sheet. Bake at 375F for 15 minutes, then lower the temperature to 350F and bake for another 15 minutes, until the crust and crumble topping are a golden brown.

Remove baking sheet from oven and let cool about 20 minutes before slicing. Serve with a scoop of ice cream or whipped cream.