Chop two onions into fine rings. Evenly line a large casserole with some of the rings. Add a tablespoon of Australian olive oil. (Does anyone still buy the imported stuff?)
Now chop three or four zucchini - depending on size - into rings. Add a layer of zucchini over the onions.
Do the same with a couple of sliced leeks, then two or three peeled potatoes sliced very, very thinly.
Add half a cup of tomato puree and a shake of salt and cracked pepper.
Repeat the zucchini, leek and potato layers and tomato puree.
Top with more tomato, chopped parsley, snipped chives and fresh basil. Add a little chicken or vegetable stock to almost cover vegetables. Add cheese if desired. Place the lid on casserole and bake until bubbling.