Preheat oven to 350 degrees F. Line a baking sheet with parchment paper or foil; set aside. In a medium saucepan, heat and stir 1-1/2 cups Ghirardelli(R) 60% Cacao Bittersweet Chocolate Baking Chips and the butter over very low heat until melted and smooth. Remove from heat. Add eggs, sugar, flour, vanilla, and baking powder. Beat with wooden spoon until combined, scraping sides of pan. Stir in remaining 1 cup Ghirardelli 60% Cacao Bittersweet Chocolate Baking Chips.
Drop dough using a small cookie scoop or by rounded teaspoons 2 inches apart onto the prepared baking sheet. Bake for 8 minutes or until edges are firm and surfaces are dull and crackled. Cool on cookie sheet for 2 minutes. Transfer to a wire rack; cool.
To assemble cookies, spread Peppermint Chocolate Filling on the bottoms of half the cookies. Top with remaining cookies, bottom sides down. Enjoy immediately or refrigerate in an airtight container for up to 3 days.
Peppermint Chocolate Filling: In a small bowl, combine cream cheese and powdered sugar. Stir in enough milk, 1 teaspoon at a time, to make a filling of spreading consistency. Stir in chopped Ghirardelli Peppermint Bark Baking Bar.