Combine flour, baking soda and salt in small bowl. Beat butter, brown sugar, sugar and vanilla in large mixer bowl. Beat in egg. Gradually beat in flour mixture. Stir in 1 cup morsels; spread into greased and wax paper-lined 9 inch heart-shaped pan. Bake in preheated 375 oven to 18 to 20 minutes or until light golden brown. Let stand for 10 minutes; remove to wire rack to cool completely. Microwave remaining morsels in microwave-safe bowl on high power for 1 minute; stir. Microwave at additional 10 to 20 second intervals, stirring until smooth. Spread over cookie. Chill for 30 minutes or until chocolate is set. Decorate as desired.