Place everything in a food processor and blend for about a minute (you might need to add a bit more water). Spread ½ cup finely chopped pistachios on a plate. Scoop cherry mixture with a tablespoon, and with wet hands, form into a ball. Roll it in the chopped pistachios and set on a separate plate. Repeat to make 18 to 20 balls. Freeze for 30 minutes and store in refrigerator.