Cut peeled potato into slices (across). Put potato into a salad bowl, pour over olive oil and vinegar dissolved with half glass water (1 dcl). (It is much better if you season warm potato because it will soak oil, vinegar and seasoning much better.)
Cut onion into thin rounds and add to potato. Add salt and pepper. At the end add hand cut basil leaves. Do not put too much basil – it must be surprise for consumer.