Stir together flour and baking soda. In a medium saucepan heat and stir brown sugar, butter, and water over low heat till butter is melted. Add chocolate pieces. Heat and stir till chocolate is melted. Pour into a large mixing bowl and let stand for 15 minutes or til cool.
Beat egg into chocolate mixture. Stir in the flour mixture till well mixed. Dough will be soft. Cover and chill for 2 hours, or till easy to handle. (If you refrigerate overnight you will need to let dough sit on counter for about 30 minutes).
Shape into 1" balls. Place 2" apart on ungreased cookie sheet. Bake in a 350 degree oven for 8 minutes. Remove and immediately top each cookie with a mint. Return to the oven and bake about 2 minutes more or till cookies are done. Swirl the melted mints with a knife to "frost" cookies. Remove and cool til mints are firm. Makes about 48.