Wash the spinach and watercress, prepare, tear into bite-sized pieces and place in a bowl or divide directly onto several plates.
Drain the mozzarella well and cut into small cubes. Wash the tomatoes, cut them in half or quarter the slightly larger pieces. Spread both on the salad.
For the dressing, mix all the ingredients together well and drizzle over the salad. If you like, you can garnish the salad with fresh basil leaves.