Preheat the griller. Bring the stock to the boil in a large saucepan then gradually stir in the polenta. Cook over low heat for about 10 minutes, stirring constantly, until the polenta is smooth and thick. Remove from the heat.
Grate the Parmesan cheese to give 3 tablespoons. Add, along with the butter, to the polenta and press the mixture into a lightly oiled 23-cm flan or quiche dish. Brush the top with a little olive oil and refrigerate for 10 minutes.
Finely slice the tomatoes and shred enough basil leaves to give about 4 tablespoons. Put aside.
When the polenta has firmed, place the flan dish under the griller and cook for 7 minutes, until golden. Remove the flan dish but leave the griller on.
Arrange the tomatoes on top of the polenta and scatter over the basil. Season the tomatoes with pepper, sprinkle with sugar, drizzle over the remaining oil and top with the prosciutto. Put the tart back under the griller for 5 minutes, until the prosciutto is crisp. Cut into wedges and serve immediately.
This tart is fine served on its own for a light meal but it also teams well with a plain grilled steak.
NUTRIENTS PER SERVING, WHEN SERVING 4:
good source of vitamins B group and C.
It's good to use good-quality, coarsely ground polenta; ‘instant’ polenta will not give the same taste result.