Heat oven to 350°F. Lightly grease 2 cookie sheets. Lightly spoon flour into measuring cup; level off. In large bowl, combine flour, sugar, brown sugar, baking powder and salt; mix well. Add melted chocolate, orange peel, oil, orange juice, vanilla and eggs; blend well. (Dough will be stiff.) Add 6 oz. chopped white baking bar; gently knead into dough.
Divide dough into quarters; shape each quarter into a log about 14 inches long. Place 2 logs on each cookie sheet; flatten each log into 2 1/2-inch width. Bake at 350°F. for 18 to 20 minutes or until firm to the touch.
Remove cookie sheets from oven. Reduce oven temperature to 300°F. Cool logs on cookie sheets 10 minutes.
Cut warm logs diagonally into 1/2-inch-wide slices. Place slices, cut side up on same cookie sheets. Bake at 300°F. for 7 to 9 minutes or until top surface is dry. Turn cookies over; bake an additional 7 to 9 minutes. Remove cookies from cookie sheets. Cool completely on wire racks.
In small saucepan over low heat, melt topping ingredients, stirring until smooth. Drizzle over cookies.