01 - Preheat oven to 350°F. Line baking sheets with parchment paper to prevent sticking.
02 - Whisk together flour, baking soda, and salt in a medium bowl; set aside.
03 - In a large bowl, use an electric mixer to cream softened butter with granulated and brown sugars until light and fluffy.
04 - Beat in eggs one at a time, then add vanilla and peppermint extracts, mixing thoroughly.
05 - Gradually add dry ingredients to the wet mixture, stirring just until incorporated.
06 - Fold in semisweet chocolate chips and half a cup of crushed peppermint candies evenly.
07 - Drop tablespoon-sized portions of dough onto prepared baking sheets, spacing them 2 inches apart.
08 - Bake for 10 to 12 minutes or until edges turn lightly golden. Cool on baking sheets for 5 minutes before transferring to a wire rack to cool completely.
09 - Beat softened butter until creamy. Gradually add powdered sugar, then milk and peppermint extract. Continue beating until mixture is smooth and fluffy.
10 - If desired, swirl in a few drops of red food coloring to achieve a festive appearance.
11 - Once cookies are fully cooled, frost each one generously with the prepared peppermint frosting.
12 - Sprinkle frosted cookies with remaining crushed peppermint candies and mini chocolate chips if using.