2) Bring vinegar to a boil in a 500ml saucepan. Reduce heat; simmer, uncovered, 9 to 10 minutes or until reduced to 75ml. Set aside.
3) Meanwhile lightly shape beef mince into 8 (1-cm) thick patties.
4) Brush polenta slices with oil. Place patties in center of griddle over medium, ash-covered coals and arrange the polenta around the patties. Grill patties and polenta, uncovered, 11 to 12 minutes or until patties are medium (70C) doneness, not pink in center and juices show no pink color and polenta is heated through, turning once and basting patties with 2 tbsps reduced vinegar after turning. Season burgers with salt and pepper, to taste.
5) For each serving, layer 1 each polenta slice, burger, mozzarella slice and tomato slice. Drizzle with remaining vinegar and sprinkle with basil, as desired.
Cook's tip: To cook over a gas barbecue, preheat barbecue according to manufacturer's directions for medium heat.
Cook's tip: If prepared polenta is not available, the following may be used--combine 750ml water, 1 tbsp butter and 1/2 tsp salt in large saucepan and bring to a boil. Gradually whisk in 150g cornmeal. Reduce heat to medium-low; cook 15 minutes, stirring often (Mixture will be very thick). Remove from heat; cool slightly. Spoon polenta on aluminum foil-line baking sheet. cover with plastic wrap and pat into 24- by 12- by 1-cm rectangle. Refrigerate 1 hour or as long as overnight. Cut chilled polenta into 8 (6-cm) circles using a cookie or biscuit cutter. Proceed as directed above.
Cook's tip: Prepared balsamic syrup, available in large supermarkets and specialty food stores, may be substituted for balsamic reduction.