Mix the shortening, sugar, egg, molasses, and water until combined.

Stir in the cream of tartar, salt, baking soda, and spices until mixed in.

Add the flour and stir until combined.

Cover with plastic wrap touching the dough and chill until firm about 1 hour.

Heat your oven to 400 degrees and grease or add parchment paper to two cookie sheets. Using a medium-sized cookie scoop, drop scoops of the cookie dough onto the prepared sheets, about 2″ apart.

Bake for 8 minutes or until only a slight indent remains when you gently press the top of a cookie with your finger. Remove from the oven and allow to cool.

To make the frosting, cream the softened butter, then stir in the powdered sugar, vanilla extract, and 1 Tbsp milk. Add 1/2 Tbsp more of milk until it reaches the desired consistency. If it becomes too thin, add 1/4 cup more of the sugar until it thickens up again.

Frost the cookies when slightly warm or cooled completely. Top with sprinkles, if desired.