Blend pesto ingredients, excluding vinegar, into a fine purée using a food processor.
Preheat the oven to 160°C.
Preheat the deep fat fryer oil to 160°C.
Boil potatoes in salted water for 12 to 18 minutes until tender and drain.
Evaporate remaining moisture over heat and mash potatoes until smooth.
Mix parmesan, pesto, sun-blushed tomatoes, basil, and seasoning into the mash.
Shape mixture into 12 cylinders and insert a piece of mozzarella into the center of each.
Coat each croquette in flour, then beaten eggs, and finally breadcrumbs.
Fry croquettes for 3 to 4 minutes until golden and keep warm in the oven.
Mix vinegar into the pesto and serve three croquettes per plate over the sauce.