Place the ice cubes in a blender or food processor and process to crush. Set aside 4 of the blackberries and add the remaining berries to the blender or food processor along with the sugar. Puree until smooth. Add the ice cream and milk, and process until smooth or to the desired consistency.
Pour into 2 tall glasses and garnish with the reserved berries. Serve immediately.
Williams-Sonoma Lifestyles Series,
Casual Outdoor Dining,
by Georgeanne Brennan
(Time-Life Books, 1998).