Mash the pre-cooked potatoes with a fork. Add in all four types of cheese, as well as the parsley.
Knead everything thoroughly together and shape it into small balls. Press them flat between your palms, and then coat them in first the flour, then the egg and finally the breadcrumbs.
Fry the cheese disks in hot oil until both sides are golden brown.
To prepare the dip, sweat the diced onion in the oil. Add the garlic, chili and tomato purée and mix it all together.
Pour in the cola and balsamic vinegar. Let the dip simmer in order to reduce it, before you pour in the sieved tomatoes.