Preheat oven to 325°.  Cream together butter and sugar until light and fluffy.  Beat in eggs, vanilla, and crème de menthe.  Add flour, baking powder, and salt and beat until well combined.  Stir in Andes and semi-sweet chips.  Line 4 baking sheets with parchment or a silicone baking mat.  Drop dough by large scoopfuls to create 1 log on each sheet, dividing dough evenly.  Using slightly damp hands shape and flatten each log into a 14” x 1 ½” log.  Bake for 20-25 minutes or until set and lightly browned.  Cool for 5 minutes on a wire rack.  While still warm slice diagonally into ¾” thick cookies and spread cut-side down onto two baking sheets.  Return to oven and bake 10-14 minutes, turning over halfway through baking time, or until slightly browned and dry.  Cool completely on a wire rack.

 If desired, melt together:

½ of another 10-oz. bag of Andes mint chips

1 c. milk chocolate chips

 Stir in a few drops of peppermint oil and dip one side of each cookie into the chocolate.  Cool chocolate-side up on a rack until chocolate is set.  Store in an airtight container.