Wash and slice the zucchini. Heat oil in a frying pan. Fry the zucchini on both sides for about 2 minutes. Season with salt and pepper. Roast slices of toast in a toaster and brush with butter.
Wash spring onion, shake dry and cut half into fine rings. Cut the remaining spring onion into long strips and place in cold water. Cut the mozzarella into slices. Cover toasts with zucchini, ham and mozzarella.
Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 4 minutes. Sprinkle with spring onions and coarse pepper.