1.Place eggplant in colander; sprinkle with salt. Stand 30 minutes; rinse well under cold water. Pat dry with absorbent paper.
2.Heat oil in large saucepan; cook onion and garlic, until soft. Add rice, stock and the water; bring to a boil. Reduce heat; simmer, covered, about 30 minutes or until rice is tender and almost all the liquid is absorbed.
3.Using vegetable peeler, cut zucchini into thin strips, lengthways.
4.Stir eggplant, zucchini, tomato and mushrooms into rice; cook about 3 minutes or until vegetables soften. Stir in half of the cheese and oregano; serve risotto sprinkled with remaining cheese.