These soft and minty cookies are perfect for your Christmas cookie snacking. Your friends and neighbors will love them, too!
Preheat oven to 350 F. Line two baking sheets with parchment paper and set aside.
In a stand mixer with the paddle attachment, mix together the cake mix, eggs, and shortening. Combine until there is no dry cake mix remaining. Scoop out batter either in rounded half tablespoon or scant tablespoon measuring spoon (using the half tablespoon will make about 25 Oreo-sized sandwich cookies, scant tablespoon amount will make bigger 16 sandwich cookies). Roll the dough into a ball and place on the cookie sheet. Bake for about 8 minutes. The cookies won't look totally baked in the middle, but that's okay! You don't want to over-bake them.
Right after you have removed the cookie sheet from the oven, give each cookie a gentle tap on top with a spatula to flatten them a bit. Let cool on the baking sheet for a few minutes, then transfer to a cooling rack.
In a stand mixer using the whisk attachment (or using a handheld mixer), cream together all filling ingredients for several minutes, scraping down the sides as you go. Let the filling whip on medium high speed for 2-3 minutes until the frosting is light and fluffy.
Pair two cookies together that are the same size, and spread the frosting in the middle. Decorate the sides with sprinkles or crushed candy cane if you'd like. These are best eaten after a couple of hours of setting and to two days afterward. Enjoy!