I made up a batch of these once and found out I had no peppermint flavoring so I used crème de menthe. It's a candy flavoring I got from a bakery store, in the cake decorating isle. What a delicious different that the peppermint. It's a softer mint flavor that adds, I think, the perfect flavor to my buttermints.
Mix all ingredients together in a medium sixed bowl. Knead until smooth, add more powdered sugar if needed, but don't make it too dry. Knead enough to resemble a ball of dough.
Can separate into smaller amounts and use the color of food coloring of your choosing.
Take small rounds of the mixture and roll into small balls. Place on waxed paper and press a fork to flatten them. Should be the size of a dime or a nickel if you like a bigger bite after pressing. Let these dry for about 48 hours if you intend to put them into a bowl. They can, however be eaten right away.