First step is to grab all of your ingredients and set them aside. Preheat your oven to 350 degrees Fahrenheit.
Grab a large baking sheet and line it with parchment paper.
Start by combing your butter and white sugar in an electric mixer. You can use a hand mixer too if this is what you have! Allow this to mix on medium speed for a few minutes until well combined and creamed together.
Once the butter and sugar have mixed well, add the egg, yogurt, eggnog and spices, in that order! Continue to mix this on medium speed until combined.
Combine the flour, cornstarch and baking soda in a separate small bowl and then gradually add this to your wet mixture and continue to mix until just combined, but don’t over mix!
Using a 1.5 – 2 tbsp sized cookie scoop will give you the best result for round cookies! Use a scoop if you have one and place the balls of cookie dough on your parchment lined sheet. These cookies don’t spread a ton, so you can usually fit 12 on a large baking sheet. Flatten these cookies about half way down from their scooped size, as they do not spread a ton, and then bake for 12 minutes.
While those bake, add all ingredients for the icing in to your mixer and mix on high speed until smooth. Icing can be tricky sometimes because all butter tends to have slightly different moisture levels. If your icing is too thick, adda splash of milk. If it is too thin, add a tbsp of powdered sugar, until you reach your own preferred texture.
Pipe the icing on to the cookies once they have cooled completed. This recipe makes 12 cookies. These cookies will keep fresh on the counter for a few days or in the fridge for a week. They are able to be frozen but best if done before icing.