Wash and clean the tomatoes and cut them into 12 slices. Dab mozzarella dry and cut into 16 slices. Wash the basil, put something aside for garnishing. Remove the remaining leaves.
Cover 4 sandwich slices with basil, tomatoes, mozzarella and ham slices, season with salt and pepper. Cover with 1 sandwich slice each. Whisk eggs and milk, season with salt and pepper.
Pour into a wide bowl. Turn the sandwich in the egg milk, press the edges together. Heat 3 tablespoons of oil in a large frying pan. Fry 2 sandwiches for 2-3 minutes on each side. Remove and keep warm.
Fry the rest of the sandwich as well. Halve the sandwich, arrange on plates and garnish with basil.