Wash the potatoes, wrap in aluminium foil and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 1 1/2 hours. In the meantime, wash the tomatoes and rocket and pat dry one by one.
Drain the olives and cut into fine rings. Halve the cherry tomatoes. Drain mozzarella and cut into small cubes. Put cherry tomatoes, olives and mozzarella in a bowl. Mix vinegar and oil, season with salt, pepper and sugar.
Take out potatoes, wrap them from the foil, cut them lengthwise in the middle until 1 cm before the edge and press them apart. Add the vinegar-oil mixture to the tomato-mozzarella salad and mix thoroughly.
Add tomato mozzarella and rocket to the potatoes and garnish with basil.