1.Whisk the water and half the mint jelly in a small bowl until smooth. Stir in yoghurt; cover, refrigerate until required.
2.Combine flour, zucchini, beetroot, onion, garlic, peas and egg in a large bowl; season. Shape mixture into 8 patties.
3.In batches, cook patties on a heated and oiled barbecue flat plate, flattening with a spatula, until browned both sides and cooked through. Transfer to tray; cover to keep warm.
4.Meanwhile, brush remaining mint jelly over lamb. Cook on heated oiled barbecue (or grill or grill pan). Remove from barbecue. Cover and stand 5 minutes.
5.Serve lamb with patties and mint yoghurt.