Sauté the diced onion with the crushed garlic cloves in a pan with a little fat until translucent, remove from the heat and allow to cool.
Mix the oil, vinegar and the finely chopped basil leaves in a bowl and sprinkle with salt and pepper. Add two thirds of the grated Emmentaler, the steamed onion and the halved mini mozzarella, season with pepper and mix everything together. Fold in the halved tomatoes and the peeled, halved and sliced potatoes and season to taste.
Arrange the salad in bowls, sprinkle with the rest of the Emmentaler, garnish and serve.