Prick each sweet potato a handful of times using the tines of a fork, which allows steam to escape from the potatoes during baking.
Wrap each potato in aluminum foil and bake them at 400 degrees F for 1 hour in a pre-heated oven. NOTE: Test for doneness by gently squeezing the middle of the potato (using a pot holder). If it gives in easily to your touch, it is ready.
Remove the potatoes from the oven and allow them to cool.
Peel the potatoes and run the flesh through your food processor, until super smooth. Run the puree through a cheesecloth, removing any extra bits. Measure out the puree in a dry measuring cup, you should have 1 cup.
Cook the sweet potato puree down by half in a frying pan on a medium-low heat for about 5 minutes. This will remove excess water from the puree. If you do not do this, your cookies will be cake-like and limp.
In a medium bowl, whisk together 3 cups of flour, 4 teaspoons ginger, 1 tablespoon cinnamon, 2 teaspoons nutmeg, 1 teaspoon clove, ½ teaspoon salt and ½ teaspoon baking soda.
With an electric mixer, beat ½ cup butter and ½ cup sugar until smooth. Beat in the sweet potato puree. Beat in 1/3 cup molasses and the egg.
Using the electric mixer on low, add in the dry ingredients until dough just forms.
Place dough on floured plastic wrap and wrap well; chill until firm, about an hour.
On floured parchment paper, roll dough 1/8 inch thick, flouring dough and rolling pin as needed. Freeze dough on paper for about 20 minutes.
Cut dough and transfer to parchment-lined baking sheet.
Bake in a pre-heated oven at 350 degrees F until firm and edges just begin to darken. About 8 minutes. Let cool completely on baking sheets.
Decorate cookies with frosting: 1 cup confectioner's sugar, 2 tablespoons milk and desired food coloring. Enjoy!