HI,How you doing.As to your question there are two ways to raise onions through the winter.One is in a greenhouse in a special seed bed.This will entail the use of sodium lighting and the need to achieve a constant temperature.Unless you intend to exhibit your onions,this is a time consuming task and not for the faint hearted.To grow outside,the first recommendation is to have a finely,broken seed bed with the constiuency finely broken so as to let water run directly through it and not drown the infant onion.In my own method of growing over wintering onions I do use cloches,as far as I have found this is good gardening sense..Then if you still want to try this method,sow the seeds 1/2 inch deep at one foot apart.When the infants are 4'' high,plan then what size of bulb you will be requiring for the table.Small globes reduce to 4'' apart,medium to 6'' apart and finally if quite large are required 12'' apart.Now please bear in mind this is only my experiences.The reason I have wrote this blog to you in answer to your question is to show you it can be done but it certainly no cake walk.I hope it goes some way in assisting you...Good Luck.Quintail.