beat butter on med/high speed for 30 sec until fluffy, then add sugar, cocoa, baking powder and salt
beat in eggs and peppermint extract
toss dark chocolate chips into your flour and add until just combined
divide dough into four equal portions, wrap tightly in plastic wrap and chill for 1 hour
preheat oven to 375°, line cookie sheets with parchment paper
roll portions of dough into 7" logs and flatten to about 2" wide
add to cookie sheet 2" apart, bake for 14-16 min
Cool on wire rack for 30-60 min
using a sharp or serated knife, slice on a diagonal into about ½" slices
reduce oven temp to 325°
lay biscotti cut side down and bake for 5 min, remove from oven, turn over and bake the other side for 5 min, remove and cool completely on wire rack
melt white chocolate according to package directions, dip one cut side of biscotti in chocolate and then in crushed peppermint, let set