In a large bowl using an electric mixer, beat together margarine, brown sugar, and Splenda Sweetener on medium speed until light and fluffy. Blend in egg and vanilla extract.
Gradually mix in flour mixture. Stir in chopped chocolate.
Drop heaping tablespoonfuls of dough 2 inches apart onto ungreased baking sheets.
Bake cookies 11–12 minutes or until lightly browned. Cool slightly, then transfer to a wire rack to cool completely.
Melt remaining 2 chocolate squares as directed on package. Stir in whipped topping and water. Dip half of each cookie into melted chocolate mixture; let stand until firm.