1 Place berries in a deep container and let thaw for about 5 minutes. Squeeze lemon.
2 Stir together the buttermilk, cinnamon, honey and 1-2 tablespoons lemon juice.
3 Add the spiced buttermilk to the berries and puree with an immersion blender until smooth. Freeze until firm, about 10 minutes. Use an ice-cream scoop to form mixture into balls. Rinse the lemon balm, shake dry and pluck leaves. Serve the ice cream sprinkled with lemon balm.