And here's a bonus I've learned: chives are perrenials! If you harvest only half of the onions, the rest will keep growing and multiply into more the next year!
Any type of onion bulb or garlic can also be growin into a full plant.
For bulb onions or garlic, simply let them sit somehwere, preferrably warm and with some light, and they will start to grow (after all, they are a bulb). For garlic, each individual clove will sprout and can be grown and will produce a whole new bulb with lots of cloves.
(Disclaimer: I have only ever grown garlic this way, so I cannot personally attest to the success of onions grown this way. Depending on the type of onion, they may in fact need two years to grow to full size. However, they are edible at any size!)
Garlic and onions are fairly cold hardy, so here in the pacific northwest farmers are already growing them out in their feilds. Some even start them in the fall and grow them over the winter!
Last year I planted garlic in my garden (simply by planting old cloves that had sprouted) and then planted pole beans among them not knowing that beans and garlic don't like each other (and also thinking the beans were the bush type). The pole beans completely smothered out my garlic, and then after I pulled out all the pole beans in the fall, my garlic all started growing again! They have been out there all winter and have kept growing even through a week of cold snow very uncharacteristc of Seattle.