1Melt butter in medium heavy-bottomed saucepan on medium heat. Cook 3 to 4 minutes or until butter forms browned specks on bottom of pan, stirring occasionally. Pour butter into large bowl. Cool slightly. Refrigerate 1 hour or until butter returns to the consistency of room temperature butter.
2Line 9-inch square baking pan with foil. Spray with no stick cooking spray. Mix flour, cornstarch, 1/2 teaspoon of the cinnamon and salt in medium bowl. Set aside. Add sugars and vanilla to browned butter; beat with electric mixer on medium speed until light and fluffy, scraping sides occasionally. Gradually beat in flour mixture on low speed until well mixed. Press dough evenly in prepared pan.
3Bake in preheated 300°F oven 55 to 60 minutes or until center is firm and edges are lightly browned. Immediately, cut shortbread into 4 squares then cut each square crosswise into 4 triangles. While still warm but not hot, remove shortbread from pan to wire rack to cool.
4Melt chocolate as directed on package. Stir in remaining 1 teaspoon cinnamon. Drizzle chocolate over shortbread triangles. Let stand on wax paper-lined tray until chocolate is set.