Preheat oven to 350°F and line a baking sheet with parchment paper.
In a large bowl, beat together butter, cream cheese, and peppermint extract until smooth.
Add powdered sugar and beat until fully incorporated. Mix in green food coloring if using.
Gradually mix in flour and salt until a dough forms. Fold in mini chocolate chips.
Roll dough into 1-inch balls and place on prepared baking sheet. Flatten slightly.
Bake for 9-11 minutes or until edges are set. Let cool completely on a wire rack.
In a microwave-safe bowl, melt chocolate wafers with shortening in 20-second increments until smooth.
Dip half of each cookie in the melted chocolate and place on parchment to set.