In a large bowl using a hand or stand mixer with the paddle attachment, mix the butter, shortening, and dark brown sugar on medium-high speed until light and creamy (about 1 minute).

Scrape down the bowl and mix in the vanilla and egg. Once smooth, scrape down the bowl again and mix in the molasses until smooth, rich, and glossy (it will look so lush at this point!).

Now mix in the spices, salt, baking soda, and cream of tartar until combined.

Scrape down the bowl and mix in the flour. Mix as long as your mixer can handle it because it will produce a very thick and sticky dough. Then remove the bowl and use a strong silicone spatula to fold the dough and ensure it’s evenly combined. This will take some elbow grease!

Dump the dough out onto a sheet of plastic wrap dusted in flour. Coat your hands in flour and pat the dough into a rectangle that’s ½″ thick. Wrap it up and chill for at least 1 hour or overnight.

When ready, remove the dough from the refrigerator once the oven has preheated to 350F.

Cut the dough in half and return one half to the refrigerator. To the other half, coat both sides in flour and roll onto a well-floured surface. Roll to ¼″ thick and cut out your cookies.

Carefully transfer the cookies to a large cookie sheet lined with parchment paper, spaced a couple inches apart.

Bake for 8-10 minutes (start with 8 and then assess). They’re done when they’re evenly puffed with a cracked surface, but still appear a little underdone in the center.

Allow to rest on the pan for a minute or two, then transfer to a cooling rack. The cookies will de-puff as they cool.

Continue baking the rest of the batch then repeat the process with the other half of dough until all the cookies are baked.

Make the icing once all the cookies have cooled. Whisk together all of the ingredients, starting with 6 tsp of water. The consistency should be slightly thicker than glue.

If it’s too thick and pasty, mix in 1 tsp of water at a time until you reach a thick glue consistency.

Mix in a drop or two of gel food coloring at this point if you like. Pipe designs onto the cooled gingerbread cookies and enjoy!