Berry-Mint Granitas

1 . Stage

Remove lemon zest in 1- to 2-inch sections using a vegetable peeler, avoiding the bitter white pith. Squeeze and reserve 2 teaspoons of juice.

2 . Stage

Stir lemon zest, water, sugar, and mint together in a small saucepan. Bring to a boil over medium heat, stirring until sugar dissolves. Let cool, 10 to 15 minutes. Transfer to a bowl and chill, covered, for 45 minutes. Remove and discard lemon zest and mint.

3 . Stage

Process blueberries and raspberries in a food processor until smooth. Strain through a fine-mesh sieve into a bowl with chilled syrup; discard seeds. Stir in reserved lemon juice.

4 . Stage

Pour berry mixture into a 9x13-inch baking pan. Cover and freeze until edges are slushy, 1 1/2 to 2 hours. Stir with a metal spoon, scraping frozen mixture off bottom and sides of pan. Cover and freeze, stirring every 30 minutes, until mixture is slushy, about 3 hours more. Cover and freeze until firm, 4 to 24 hours more.

5 . Stage

Let stand and soften slightly at room temperature, 5 to 10 minutes. Scrape surface of granita with a fork and spoon into chilled dessert dishes.