For the peach parfait, puree 350 g pitted peaches, the yogurt and the sugar with a blender. Roughly dice 250 g pitted peaches.
Soak the gelatine in cold water. Heat 8 tablespoons of peach-yogurt puree in a saucepan and dissolve the squeezed gelatin in it.
Quickly fold into the remaining peach-yogurt mixture with a whisk. Whip 200 ml of whipped cream until stiff, chop the lemon balm and fold both into the peach-yogurt mixture.
Line a loaf pan (1 liter capacity) with plastic wrap, pour in the amount and freeze for at least 6 hours.
Allow to thaw at room temperature for 1 hour before serving.