Mash the ricotta with a fork. Add milk and eggs and mix well. Cut basil leaves into strips. Add to the egg and cheese mixture. Season with salt and pepper. Clean, wash and slice the tomatoes.
Heat a tablespoon of oil in a frying pan. Add a quarter of the tomato slices, fry briefly and add a quarter of the egg and cheese mixture to each. Leave to set at medium heat. Turn with the help of a lid and bake on both sides until golden brown. Fry a total of four frittata in hot oil. Arrange each frittata with two slices of ham on a plate