Combine first 3 ingredients in a large saucepan; cook over low heat until chocolate melts and mixture is smooth, stirring occasionally. Remove from heat, and stir in 1/2 cup crushed peppermint and 6 Tbsp. sugar. Let cool 30 minutes.
Add eggs to melted chocolate, 1 at a time, stirring well. Stir in extracts.
Combine flour, baking powder, and salt; add to chocolate mixture, stirring until combined. Stir in chocolate morsels. Cover and chill dough 2 hours or until firm enough to shape.
Shape dough into 1 1/2" balls; place on parchment paper-lined baking sheets. Bake at 325° for 12 to 13 minutes or until cookies are puffed and cracked on top. Sprinkle coarsely crushed peppermints onto cookies; press candy lightly into cookies. Let cookies cool 5 minutes on baking sheets. Transfer to wire rack to cool completely.
Whisk together powdered sugar and milk; drizzle over cooled cookies, if desired. Drizzle with melted chocolate, if desired. Sprinkle cookies again with chopped peppermint, if desired. Let cookies stand until glaze and chocolate are firm.