Cream the butter and corn syrup together. Mix in the peppermint extract, food coloring, and pinch of salt. (If you’re doing multiple colors of dough, add the coloring after adding the powdered sugar.)
Add the confectioners’ sugar, one cup at a time. Beat on low until incorporated to keep the powdered sugar from flying all over. Then, beat on medium-high speed until the mixture is smooth and creamy.
Knead with your hands to incorporate any last bits of sugar or dough.
If you’re making multiple colors, divide the dough in half (or however many colors you want), and add the food coloring to each piece, starting with 1 drop and kneading, adding 1 drop at a time, until the desired colors are reached. Gather each piece of dough into a ball.
Shape the dough. While you work, keep the bowl loosely covered in plastic wrap to prevent them from drying out.
Using a cookie dough scoop, make small balls of dough. Flatten the dough ball with the bottom of a glass that’s been dipped in powdered sugar, or with the palm of your hand.
Use your hands, dusting them with confectioners’ sugar as needed to reduce any stickiness to make the dough into any shape you like.
Allow the candies to dry at room temperature, uncovered, overnight.
Video
Notes
Store the buttermints, layered between parchment or wax paper, in an airtight container at room temperature for up to 2 weeks.
Refrigerate up to 1 month. For longer storage, store in freezer up to 2 months.