1. Pour 1 1/4 cups coffee into an ice cube tray or trays and freeze until solid, at least 3 hours.
2. To a blender (through opening in lid) or food processor with motor running, add frozen coffee cubes, chocolate syrup, nonfat dried milk, and 1/4 cup cold coffee. Whirl until mixture is a thick slush; if thicker than you like, add a little more cold coffee. Pour into tall glasses.