Preheat oven to 350 degrees F
Line a baking sheet with parchment paper or silicone mat
In a large bowl, beat the butter until fluffy
Add sugar and salt and beat until well combined and fluffy
Beat in the egg and vanilla until well combined
Gradually add the flour and beat until well combined
Add food coloring and peppermint extract and mix very well
Roll into balls and place on prepared baking sheet
Lightly press down each cookie ball using a flat bottom glass dipped in water
Sprinkle lightly with granulated sugar if desired
Bake for 8-10 minutes or until edge are set and slightly golden brown
Remove to wire rack and cool completely
Crush peppermint in a resealable bag using a rolling pin
Melt chocolate in microwave safe bowl
Dip edge of cookie into chocolate and immediately add crushed peppermint
Set on wire rack to set
Store in airtight container