Heat the oil in a large heavy-bottomed pan until a breadcrumb sizzles and turns brown in it (CAUTION: Hot oil can be dangerous, do not leave unattended).
When oil is hot, use a teaspoon to drop tablespoonfuls of polenta into the oil and deep-fry for two minutes, or until golden. Carefully remove the polenta pieces with a slotted spoon and drain on kitchen paper and keep warm.
To make the sauce, in a separate pan heat the oil, garlic and onion together for two minutes.
Add the tomatoes, basil and prosciutto and cook for five minutes.
Add the mozzarella and spinach to the pan and stir for 1-2 minutes, or until the spinach has wilted.
To serve, place the polenta onto a warmed plate and pour the sauce over it.