Wash the arugula, drain and transfer to a large bowl. Quarter the mini mozzarella balls. Carefully pluck the ham into small pieces and add both to the bowl with the rocket.
Cut the tomatoes into cubes and remove the seeds. Dice the onion or cut into thin rings. Put both ingredients in the bowl as well.
Now season to taste with the olive oil, balsamic vinegar, salt and pepper.
Finally add the parmesan and mix everything well.
Tip: To make eating the salad easier, you can cut the rocket 1-2 through to have smaller pieces.