Turn a favorite holiday flavor into pretty peppermint sandwich cookies and serve them up at a cookie exchange, holiday party, or potluck.
In a large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Add sugar and salt. Beat until combined, scraping sides of bowl occasionally. Beat in egg and vanilla until combined. Beat in as much of the flour as you can with the mixer. Using a wooden spoon, stir in any remaining flour.
Divide dough in half. Leave one half plain. Tint the remaining half with desired amount of food coloring. Cover each portion and chill about 1 hour or until dough is easy to handle.
Preheat oven to 375°F. Shape each portion of dough into 1/2-inch balls. Roll together one plain ball and one red ball. Place on an ungreased cookie sheet. Press with the bottom of a sugared glass until about 1/4 inch thick. Repeat with remaining dough, placing balls 2 inches apart on cookie sheet. Bake for 8 to 10 minutes or until edges are light brown. Transfer to wire racks; cool.
Spread Peppermint Filling on bottoms of half of the cookies, using 2 teaspoons for each cookie. Top with the remaining cookies, bottom sides down.
Layer sandwich cookies between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.
In a medium mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Beat in peppermint extract. Gradually beat in powdered sugar. Beat in enough milk to make a filling of piping consistency.