Wash, halve and stone the peaches. To garnish, cut 6 nice slices and put aside. Cut the remaining peaches into large pieces. Puree the peaches, lime juice and brown sugar with a hand blender.
Wash the rosemary, shake dry and pluck into 6 parts. Divide the fruit puree into glasses, fill each with 4 cl gin, mix and top up with lemonade. Garnish with peach wedges and rosemary.