Heat oven to 350°F. Line two 9-inch pie pans with aluminum foil so foil extends over sides of pans; spray foil with nonstick cooking spray. In large bowl, beat sugar and butter until light and fluffy. Lightly spoon flour into measuring cup; level off. Stir in flour and remaining cookie ingredients; mixwell. Dough will be crumbly. Divide dough in half; press in bottom of lined pans.
Bake at 350°F. for 18 to 22 minutes or until light golden brown. Cool in pan l0 minutes; remove cookies from pan by lifting foil. Cut each shortbread into 16 wedges while warm; run knife around edge of pan to loosen.
In small bowl, combine all glaze ingredients, adding enough milk for desired drizzling consistency. Drizzle over cooled cookies. Carefully remove from pan. Store in loosely covered container.