Pulse 1 cup butter, flours, and granulated sugar in a food processor 10 to 15 times or until crumbly. Press mixture evenly into a 15- x 10-inch jelly-roll pan coated with cooking spray for baking.
Bake at 350° for 18 to 20 minutes or until light golden brown.
Stir together remaining 1/2 cup butter, condensed milk, and corn syrup in a 2-quart heavy saucepan over low heat 4 minutes or until butter is melted and mixture is blended. Add brown sugar, and cook, stirring constantly, 25 to 30 minutes or until caramel colored and thickened. Pour evenly over baked cookie in pan, and spread into an even layer. Chill 30 minutes or until caramel is set.
Microwave morsels in a small glass bowl at HIGH 1 minute or until almost melted. Stir until smooth. Spread over caramel layer in pan. (The chocolate layer will be thin.) Chill 15 minutes or until chocolate is firm. Cut into 2-inch squares; if desired, cut each square into 2 triangles.
*3/4 cup all-purpose flour may be substituted.