For the crostini, sauté the onion, garlic, mushrooms, bacon and chicken liver in butter. Allow to cool, season and pass through a meat grinder once with parsley and the piri-piri.
Spread the buns with the mixture. Top with the tomato and mozzarella and bake in the oven until the cheese melts.
Arrange salad with dressing and crostini on a plate.