Onions are a member of the huge allium family that also include chives and garlic. They provide us with an invaluable resource in cooking, providing varying intensities of sweetness and pungency, generally summer harvest onions tend towards the sweetness whereas the autumn harvest ones tend towards pungency. Added raw in small amounts they make a dish come alive, but when slow cooked their natural sweetness comes to the fore and the pungent flavours are mellowed. Personally yellow onions are best for use in cooking, followed by white which are a little mellower and finally red, although red are probably the best large onion to use raw, although I would advise sparingly. Scallions and spring onions are generally used fresh, but do not be afraid of using them in cooked dishes where you want a mild onion taste, likewise small Cippolini onions are great raw or roasted.