Using an electric mixer beat egg whites and salt until light and foamy.
Keep the mixer running. Gradually add the sugar in three additions. Beat for 2 minutes between each addition.
Continue to beat until firm peaks form.
Add the powdered sugar and peppermint extract. Beat to blend, about 1 minute.
Spoon meringue into a pastry bag fitted with a ½" tip. Pipe into 1" rounds onto prepared baking sheet. Space them 1" apart.
Bake until dry. This will take approximately 2 ½ hours. Let cool completely, about 1 hour. They will crisp as they cool.
To add color: Dot drops of food coloring on the surface of the meringue. Do not stir it in. It will become swirled when piped. For stripes, paint paste food coloring along the inside edges of your pastry bag before adding the meringue. (Use a disposable bag as this will permanently stain the bag.)MAKE AHEAD: These can be made 2 days ahead. Store in an air tight container between sheets of parchment paper.Adapted from Bon Appetit magazine, Dec 2011.