Step 1
Preheat oven to 350 degrees F (175 degrees C). Line two baking sheets with parchment paper.
Step 2
Beat white sugar butter and cocoa powder together with an electric mixer in a large bowl until creamy and smooth. Add eggs one at a time beating well after each addition. Mix chocolate liqueur and peppermint extract into the sugar-egg mixture.
Step 3
Combine flour baking powder and salt in a separate bowl. Slowly mix flour mixture into sugar-egg mixture until fully incorporated; fold mint chocolate chips into the dough.
Step 4
Divide dough into 4 equal parts and shape into logs. Arrange the logs on the prepared baking sheets.
Step 5
Dip a spatula in water and use it to smooth surface of the logs.
Step 6
Bake biscotti logs in the preheated oven until firm to the touch 30 to 35 minutes. Cool biscotti logs completely on wire racks.
Step 7
Reduce oven temperature to 300 degrees F (150 degrees C).
Step 8
Cut biscotti logs into 3/4-inch slices and arrange on baking sheets.
Step 9
Bake in the oven until biscotti are dry about 10 minutes per side. Cool completely on wire racks.
Step 9
Place candy melts in a wide microwave-safe bowl; heat in microwave until melted about 2 1/2 minutes stirring every 30 seconds.