Start by adding the stick of butter to a stand mixer or a bowl with a hand mixer and mixing until creamy in texture. Then add in the powdered sugar. It helps to add it in and mix it one cup at a time.
After the four cups of powdered sugar have been added, the texture of the mixture should feel like playdough. If the butter mint dough is too greasy, add about a tablespoon more of powdered sugar as needed. If the butter mint dough is too dry, add another tablespoon of heavy whipping cream as needed.
Then, add a few drops of food coloring to the mint dough. Mix until you achieve the desired color, adding more food coloring if you want.
Next, grab a handful of the mint dough and roll it into a rope like shape about 1/2 inch thick.
Use the small knife or bench scraper to cut the rope into 1/2 inch "pillow shapes."
Repeat until all of the mint dough has been shaped.
Then, line the cooling rack with parchment paper and spread the butter mints out on it to dry for 12-24 hours.
You will know when the butter mints are done because they will be firm to the touch, but creamy on the inside. :)