In a bowl, combine the flour and the almond flour. Add the cinnamon. Set aside.
In the bowl of your mixer, add the butter, vanilla, sugar, and sea salt. Mix with the paddle for 2 minutes on medium speed. Scrape the bottom of the mixing bowl with a rubber spatula to make sure that all ingredients are mixed together. Add the egg and mix for another 2 minutes.
Add the dry ingredients (flour, almond flour, and cinnamon) and mix until they just come together. Stop, scrape the bottom and sides of the bowl and the paddle, then beat again just until the dough is well combined. Do not overmix or you will activate the gluten and the dough will be rubbery.
Scrape the dough out of the mixer and divide into 2 equal pieces. Wrap onto a sheet of plastic wrap and gently press each piece until it is about ½ to ¾ inch thick. Wrap airtight and refrigerate for at least 2 hours or overnight (this allows to the flour to absorb water in the dough, making it easier to roll out).
When you are ready to use the dough, put the rack in the middle of the oven and preheat the oven to 325 F. Line the sheet pan with parchment paper.
Take one of the pieces from the fridge and cut in half. Leave one portion at the room temperature and place the other half into the fridge (it is easier to roll one small piece at a time).
Lightly dust your work surface and roll out to 3/16 of an inch (roughly 0.5 mm). Cut into shapes with the cookie cutters of your choice and place them on the sheet pans.
Lightly brush each cookie with egg wash. Avoid letting it drip down the sides of the cookies. Let sit for 10 minutes and apply a second thin layer of egg wash.
Bake for 15 to 20 minutes, reversing the pan front to back halfway through until they are golden brown throughout. Transfer them to a rack and allow to cool completely before storing them in an airtight metal container.