Line a 7x3x2-inch loaf pan with plastic wrap. Spoon ice cream into a large bowl. Let stand for 10 minutes to soften slightly. Stir in chopped Ghirardelli(R) Peppermint Bark Baking Bars. Transfer ice cream to the prepared loaf pan. Cover and return to the freezer about 2 hours or until firm. When firm, remove from pan and wrap in plastic wrap. Freeze overnight.
Preheat oven to 350 degrees F. Grease bottom and 1/2 inch up sides of two 7x3x2-inch loaf pans; set aside. In a food processor or blender, process or blend the 1/2 cup Ghirardelli 60% Cacao Bittersweet Chocolate Baking Chips until very finely chopped (do not overprocess or the chocolate will begin to melt); set aside.
In a large bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add brown sugar, baking soda, and salt; beat until combined, scraping bowl occasionally. Beat in egg and vanilla until combined. Beat in the finely chopped bittersweet chocolate. Beat in sour cream. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour with a spatula or wooden spoon.
Divide batter among the prepared loaf pans. Bake for 40 minutes or until tops spring back when lightly touched. Cool for 10 minutes; remove from pan. Cool completely on wire rack. For easier slicing, wrap in plastic wrap and let stand overnight at room temperature.
Chill two small trays. Slice each cookie loaf into 16 thin slices. Remove ice cream from the freezer and quickly cut into 16 slices. Place a slice of ice cream between two slices of cookie. Place sandwiches on chilled trays. Freeze at least 30 minutes. Working with half at a time, trim crusts from each sandwich. Cut each sandwich in half. Place mini sandwiches in a plastic freezer container. Cover and freeze for up to 3 days.
Just before serving, prepare topping. In a small saucepan, bring whipping cream just to a boil over medium heat. Remove from heat. Add 3/4 cup Ghirardelli 60% Cacao Bittersweet Chocolate Baking Chips; do not stir. Let stand for 5 minutes; stir until smooth. Cool for 15 minutes. Remove ice cream sandwiches from freezer. Top each sandwich with 1 of teaspoon topping. Enjoy immediately.