In the bowl of a stand mixer fitted with the paddle, cream the butter until light and fluffy (about 5 minutes). Scrape down the bowl as needed. *If you don't have a stand mixer, allow the butter to come to room temperature before creaming with a hand mixer.
Add the light brown sugar and mix until just combined with the butter.
Add the molasses, eggs, and sourdough discard and mix until fully combined and there are no lumps.
In a medium sized bowl, whisk together the flour, cinnamon, all spice, ginger, salt, and cornstarch.
With the mixer on low speed, add the dry ingredients to the wet ingredients a 1/2 cup at a time. Allow the dry ingredients to almost fully mix between each 1/2 cup.
When all of the dry ingredients have been fully mixed the dough is done. Do not over mix. This dough is on the stickier side.
Divide the dough in half and roll out each half 1/4 “ thick using two sheets of parchment paper. One for under the dough and one for on top so that the rolling pin does not stick to the dough.
Place the rolled out dough in the refrigerator for at least two hours or overnight.
When you are ready to bake, preheat the oven to 375 degrees and line the baking sheets with parchment paper.
Remove one of the chilled dough sheets from the refrigerator and using cookie cutters, cut out your desired gingerbread shapes. Place the cookies on the baking sheet about 2 inches apart.
Between batches, put the cookie dough back in the refrigerator to keep cold. You can also cut out all of your desired shapes and then put the cut out raw cookies back in the refrigerator until they are needed.
Bake for 10-12 minutes or until the edges look set and the tops are no longer shiny. My cookies were perfectly done in 12 minutes.
Allow the cookies to cool on the cookie sheet for 2 minutes and then transfer them to a cooling rack.
For each new batch of cookies that you bake, use a cold or room temperature baking sheet. Do not use a warm or hot one that has just come out of the oven.
Allow the cookies to cool completely before decorating with icing.
To make the icing, use a medium sized bowl and add the warm water and meringue powder and whisk together. Add the powdered sugar a 1/2 cup at a time, mixing so that there are no lumps. You do not want your icing to be too thin or it will be hard to decorate the cookies. If it is too thin, add powdered sugar 1/2 tablespoon at a time. If it is too thick, add more warm water 1/4 teaspoon at a time.
To decorate the cookies, put icing into a piping bag and cut a small hole in the end. Decorate using royal icing and sprinkles if desired.
Notes
*This recipe calls for cubed and chilled butter that is creamed with a stand mixer. This helps maintain a sturdy dough that holds its shape for cut-outs, while still incorporating air for a tender bite. If you don't have a stand mixer, allow the butter to come to room temperature before using a hand mixer to cream it.-To store leftover cookies at room temperature, place completely cooled cookies between pieces of parchment paper in a glass airtight container for up to 7 days.-To freeze, place undecorated cookies in a freezer safe, airtight container or bag for up to 3 months. When ready to eat, thaw at room temperature.