To make the croquettes, peel and cut the potatoes into cubes.
Boil in salted water for 15 minutes or until tender.
Drain the water, mash them and allow them to cool completely.
If you use leftover mash, just add it to a large bowl and add the ham, cheeses, salt and pepper and spring onion chopped finely.
Use you hands to shape rolls out of the potato mixture, then chill them in the fridge to firm up for 20-30 minutes.
Use 3 different bowls for flour, breadcrumbs, and a third one for the eggs, which will be beaten well.
Dip each croquette in flour, shaking off any the excess, then dip in the eggs, and coat in breadcrumbs.
Heat up the oil on a medium heat, until it's sizzling hot.
Deep fry the croquettes in batches, about 2-3 minutes until golden. If you use less oil, and they are not completely covered in oil, use a fork to turn them around so they can fry evenly.
Transfer to a plate lined with kitchen paper to absorb the excess oil.
Serve hot or cold with your favourite sauce or ketchup.