Boil the potatoes in salted water. Cook over medium heat for about 20 minutes. In the meantime clean and wash spring onions and cut them into rings. Wash and halve the cherry tomatoes. Wash parsley, dab dry and cut into fine strips, except for a little bit for garnishing.
Mix vinegar, sugar, mustard, salt and pepper. Gradually add 4 tablespoons of oil. Drain the potatoes, rinse and cool. If necessary, beat the escalopes a little flatter, season with salt and pepper.
Whisk the egg in a deep dish. Put flour and breadcrumbs separately on 2 flat plates. Turn the cutlets first in flour, then in egg and finally in breadcrumbs. Peel and slice the potatoes.
Mix the potatoes with the tomatoes, spring onions, parsley and vinaigrette and leave to stand. Heat 3 tablespoons of oil in a pan. Fry the escalopes for about 4 minutes on each side. Wash the lemon, rub dry and cut into slices.
Arrange cutlets and potato salad on a plate. Garnish with parsley and lemon slices.