Sweet Potato Sugar Cookies with Fluffy Marshmallow Icing

Prepare the Sweet Potato Cookie Dough
-1 Combine the butter and sweet potato puree in a large bowl, beating together with a hand or stand mixer.
-1 Add the sugar, vanilla extract, egg, apple cider and white vinegar, mixing until well combined.
-1 Sift dry ingredients together into another bowl - flour, baking powder, baking soda, salt and cinnamon - and whisk together.
-1 Fold dry ingredients into the wet ingredients, stirring until just combined. The dough should be somewhat sticky, but not so sticky that it will be hard to work with.
-1 Divide the dough into two rounds, and wrap in plastic wrap. Transfer to the refrigerator.
-1 Let the dough chill in refrigerator for 2-3 hours.
Prepare the Fluffy Marshmallow Icing
-1 In a large clean bowl, beat the egg white, corn syrup, cream of tartar and salt together on high speed. The mixture will thicken and nearly double in volume in about five minutes.
-1 Reduce to mixer speed when the mixture has thickened like this, an mix in the powdered sugar and vanilla extract.
-1 Beat until the ingredients are thoroughly combined and thick.
-1 Cover, and transfer to the refrigerator until it is time to ice the cookies.
Bake the cookies
-1 Preheat the oven to 350°F. Line a large baking sheet with parchment paper, and set aside.
-1 Roll the dough on a well-floured surface into ½" thickness, then cut into desired shapes using cookie cutters.
-1 Transfer the cookies onto the prepared baking sheet.
-1 Bake for 10-12 minutes, or until cookies have cooked through and have firmed up. You do not want them to brown, so please keep an eye on them.
-1 Let the cookies cool on a wire cooling rack.
Ice the cookies
-1 Once the cookies are cool, ice with Fluffy Marshmallow Icing, and enjoy!
-1 Unless you're planning on eating the entire batch in one sitting, ice the cookies as you go, as the icing can soak into them and make them even softer. (Unless, of course, you like that kind of thing!)