Wash the potatoes, wrap in aluminium foil and cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 1 1/4 hours. Remove potatoes from the oven, remove foil.
Let the potatoes cool down a little. In the meantime wash and clean the tomatoes and cut them into 24 slices. Drain mozzarella and cut into 24 slices. Cut olives into slices. Halve potatoes lengthwise.
Cover with mozzarella and tomato slices. Place in the oven at the same temperature for another 5 minutes until the cheese has melted. Pluck the basil leaves from the stalks, wash and pat dry.
Arrange 2 potato halves on each plate, garnish with basil and olives.