- 2 1/2 cups raspberries (6 ounces)
- 3 cups blueberries (10 ounces)
- 1/2 cup sugar
- 1/2 cup water
- 8 cups lightly packed shaved ice (made with an ice shaver, preferably manual)
- Special equipment: an ice shaver, preferably manual
- Coarsely mash 1 1/2 cups raspberries and 2 cups blueberries with sugar and water in a 2- to 3-quart heavy saucepan using a potato masher. Bring to a boil, stirring, then boil, uncovered, stirring occasionally, 3 minutes. Transfer to a blender and purée until almost smooth, about 1 minute (use caution when blending hot liquids). Pour berry mixture through a fine-mesh sieve into a bowl, pressing lightly on and then discarding solids. Cool syrup, uncovered, then chill, its surface loosely covered with plastic wrap, until cold, about 1 hour.
- For each serving, spoon 3 tablespoons syrup over 1 cup lightly packed shaved ice and top with 1/4 cup of remaining mixed berries. Serve immediately.