In bowl, mix together blackberry fruit pulp, 1 cup water and sugar, stirring until sugar dissolves. Transfer fruit pulp mixture to shallow glass baking dish; cover.
Freeze, stirring with a fork every 30 minutes, scraping the edges of the plate and breaking up large clumps ice, until ice shards are light and fluffy and not frozen solid, about 3-5 hours.
To serve, divide granita evenly among serving glasses; top with whipped cream, if desired.
If you had to step out of the house and your granita froze solid, you can still transform it into a light, icy treat. Here’s how: Break frozen blackberry mixture into small pieces. Transfer ¼ fruit pieces to bowl of blender. Puree until the mixture becomes light and fluffy, 5 -10 seconds. Repeat with remaining pieces.