In a blender or food processor, combine the prunes and hot water until pureed. In a large bowl, combine prune mixture, 1 cup sugar, molasses and egg; blend well. Add flour, baking soda, cinnamon, ginger, cloves and salt; mix well. Cover with plastic wrap; refrigerate 2 to 3 hours for easier handling.
Heat oven to 350F. Shape dough into 1-inch balls; roll in 1/4 cup sugar. Place 2 inches apart on ungreased cookie sheets.
Bake at 350F for about 10 minutes or until set. Cool 1 minute; remove from cookie sheets.