Carve tomatoes crosswise, briefly boil water over them and peel off the skin. Cut tomatoes into quarters, remove seeds and dice. Wash basil and dab dry. Peel 2/3 of the basil leaves and cut into strips.
Mix vinegar, salt, pepper and a pinch of sugar and add the oil. Mix in diced tomatoes and basil. Clean, wash and slice the mushrooms. Heat the fat in a pan and fry the mushrooms in it until golden brown.
Arrange ham and mushrooms on plates and cover with vinaigrette. Garnish with remaining basil. Italian baguette tastes good with it.