Combine all the ingredients in a large stock pot and bring to a boil over high heat. Reduce heat and simmer for 1 hour, skimming if necessary. Strain through a china cap layered with cheesecloth, and discard the remainder. Cool the stock in an ice-water bath, transfer to a storage container and refrigerate overnight. The next day, skim off any fat that has risen to the top. Freeze any leftovers.