This salad is very simple, so the quality of each ingredient is key. Use the best olive oil and sea salt you can find, and look for buffalo mozzarella that has a wonderful tangy taste.
Place mache on a platter, and arrange mozzarella and radishes on top. Sprinkle with scallions. Just before serving, season with salt and pepper, and drizzle with the oil.
Other fresh mozzarella (made from cow's milk), including bocconcini, can be substituted.