Wash tomatoes, dab dry, cut into 12 thick slices, season with salt and pepper. Peel onion and cut into thin rings. Drain mozzarella and cut into 12 slices. Wash the rosemary, shake dry and pluck the lower needles from the twigs.
Chop about 1/4 of the plucked needles (use the rest for other purposes, e.g. drying). Set rosemary twigs aside. Wash the basil, dab dry and pluck the leaves
Clean and wash the aubergines, dab dry and cut into 24 thick slices (approx. 1.5 cm). Mix olive oil and rosemary. Spread the aubergines with the rosemary oil and sprinkle with salt. Grill for 8-10 minutes on the preheated grill while turning.
Grill half of the aubergine slices from one side only (4-5 minutes), then remove from the grill briefly and cover the grilled side with tomato slices, onion rings, mozzarella and basil. Cover with the slices of aubergine grilled on both sides and stick together with the rosemary sprigs. Place on the hot grill again for about 4 minutes. Arrange 2 turrets on each plate