Make the dough: Mix the dough together in a medium bowl. Use a stand mixer and paddle on low speed, or mix by hand—the dough comes together easily with no machine at all! Mix until no dry areas of flour remain and the butter has disappeared into the dough.
Dump the dough onto your work surface, knead it briefly by hand, and pat firmly into a flattened disc. Wrap snugly in saran wrap and refrigerate for 3 hours or more, or freeze for up to 6 months (defrost overnight in the fridge before rolling).
To proceed, let the dough sit at room temperature until it can be rolled out without cracking, about 20 minutes. While you wait, heat your oven to 350℉. Prepare 2 baking sheets, either greased with butter or covered with parchment paper.
Prepare the toppings: Beat the egg and salt together briskly to make egg wash. Combine the sugar and cinnamon. Have the chopped almonds close by.
Roll and cut: Roll the dough out ⅛ inch thick on a floured work surface. Work efficiently so the dough doesn't become too warm and sticky. If it does, chill it for a few minutes until firm and workable.
Use a 2 to 3-inch round (or heart-shaped, for a non-traditional look) cookie cutter to cut out cookies, placing them on the pans one inch apart. Gather and re-roll the dough scraps, chill briefly, and cut more cookies. Repeat until all dough is used up.
Brush the entire top of each cookie with egg wash. Sprinkle a circle of cinnamon sugar on each one, leaving the edges bare, and top with chopped almonds.
Bake for 12-14 minutes, or until light golden (start checking at 10 minutes). Rotate the pans halfway through the baking time. Let the cookies rest for 5 minutes on the pans, then transfer to a cooling rack. Cookies will keep for up to a month in an airtight container.