In a large bowl, cream butter and sugar until light and fluffy. Beat in egg: Beat in molasses, and buttermilk. Combine the flour, baking powder, baking soda, cinnamon, ginger and salt; gradually add to creamed mixture and mix well. Stir in the walnuts, raisins and dates. Chill for 2 hours or until easy to handle.
On a floured surface, roll out dough to 1/4-in. thickness. Cut with a 2-1/2-in. round cookie cutter.
Place on greased baking sheets. Bake at 350° for 12-15 minutes. Cool completely.
For frosting, beat all ingredients in a small bowl until smooth. Spread over cooled cookies; let dry completely. Yield: 5-6 dozen.