- 4 cups blackberries (about 18 ounces)
- 1/2 cup sugar
- 1 tablespoon crème de cassis (black-currant liqueur; optional)
- 1 tablespoon fresh lemon juice
- Pinch of kosher salt
- 1/2 cup mascarpone
- 1/4 cup heavy cream
- 2 tablespoons sugar
- 1 tablespoon fresh lemon juice
- 1/8 teaspoon vanilla extract
- 1/2 teaspoon finely grated lemon zest plus more for garnish
- 1 1/3 cups blackberries (about 6 ounces), cut in half crosswise
- Purée blackberries, sugar, crème de cassis, if using, lemon juice, salt, and 1 cup water in a blender until smooth. Strain purée through a fine-mesh sieve into a 13x9x2″ baking pan, pressing on solids.
- Freeze mixture until edges begin to set, about 30 minutes. Using a fork, scrape to break up frozen portions. Freeze, scraping and breaking up mixture every 20-30 minutes, until mixture resembles fluffy shaved ice, 2-4 hours.
- DO AHEAD: Granita can be made 3 days ahead. Cover with plastic wrap and keep frozen. Scrape before serving.
- Just before serving, whisk mascarpone, cream, sugar, lemon juice, vanilla, and 1/2 teaspoon lemon zest in a medium bowl until soft peaks form.
- Serve granita topped with lemon cream, halved blackberries, and more lemon zest.