I can still remember the first Farmers' Produce Auction I went to in Mt. Hope, Ohio. The items for sale that most impressed me were the crates of Candy onions. They were big and round and looked pretty as a picture-- too pretty, almost, to be real.
Last year I tried to grow them (from starter plants that came in bunches) in my vegetable garden, with not much luck. My planting was delayed, and the plants had dried up a good bit in the bundle before they were planted. This year I'm going to try to grow them from seed under lights, transplanting them when the soil can be worked.
My last expected frost is May 5th, so the time to seed them indoors is now through February 10th. If your last frost date differs from mine, check out this chart from Johnny's Selected Seeds and plug in your frost date. This will give you a planting timetable specific to your area.
I will plant them in a premoistened soilless seeding mix (I use Metro-Mix® 360 from Sun Gro Horticulture, but other soilless seeding mixes would work as well.) I'll moisten the top layer before I plant, then I'll cover them lightly with soil, press the soil gently to make sure the seed is in good contact with the soil, and water them with a plant mister so that I don't take a chance that the seeds might be dislodged by the water. I'll put them under lights and on a heat mat until they germinate, which may take a week to 10 days. I'll check them daily and water (again with the mister) when the soil begins to dry out.