If you are making your pie crust from scratch, follow the pie crust instructions below. If you are using already made pie crust, go to making the filling section.
Mix all your dry ingredients into a large bowl
Cut in your cold butter that has been sitting in your refrigerator. To do this, use a pastry cutter or pulse in a food processor until your butter is about the size of peas.
Now add your egg and water and mix until the dough starts to come together. Coming together means that you can pick up a chunk of your dough, squeeze it together and it stays together. You may need to add a little more water if this does not happen.
Once yor dough has come together, dump out on to a lightly floured board and shape into a ball. Divide the ball into 2 discs and wrap each disc with plastic wrap.
Refrigerate dough for 20-25 minutes to make the butter cold again (this helps with flakey layers). You can freeze one disc since you only need one for this recipe.
Once dough has been refrigerated, take one of your pie discs and roll it out on to a lightly floured surface to about ⅛-1/4 inches thick. Place the rolled out dough on to a sheet pan and set aside.
Making the Filling
Prepare your apples by peeling the skin, coring it and then slicing them into about ⅛-1/4 inch slices.
Add the apple slices to a bowl and squeeze ½ a lemon and toss well.
Now add your granulated sugar and cinnamon and toss it all together then set aside.
Take your apples and place them on to the rolled out pie crust leaving a 1 inch border on the outsides and making sure the apples are only slightly overlapping.
When you are done adding your apples to the crust, fold the edges over towards the middle of your pie crust making sure to only overlap the filling a little bit.
Make an egg wash by beating one egg.
Brush your egg wash over the edge of your galette.
Sprinkle the edges with a little granulated sugar.
Place in the oven and bake for 40-50 minutes or until the apples are tender and the galette edges are golden brown.
Remove from the oven and let cool for 10 minutes. Start making your brown butter frosting while your galette is cooling.
Making the Brown Butter Frosting
In a small sauce pan melt your butter over medium low heat.
Once the butter is fully melted, continue letting it cook over medium low heat until it starts to turn a golden brown color. Little specks of dark butter may form and that is ok.
Once your butter has browned, remove from the heat and stir in your vanilla and powdered sugar.
The consistency should be thin enough to drizzle. If your frosting is too thick, add ¼ teaspoon of water at a time and mix well. Keep doing this until you achieve the right consistency.
Drizzling the browned butter over your galette
Once you have made your brown butter frosting, pour the frosting into a small bowl.
Grab a fork or a spoon and dip it into the frosting and then drizzle over the top of your galette making sure to move back and forth over the galette as the frosting drizzles down.
Keep doing this until you are happy with the amount of frosting on your galette. Just make sure you can still see some of the apples poking through.
Let set up for 5 minutes.
Serve and enjoy.
This dough can be made ahead of time and stored in the refrigerator until ready or frozen. If freezing, to thaw just place frozen dough in the refrigerator overnight.