Sanitize all work areas, cutting boards, equipment and sinks used in the preparation of this recipe.
In a hot cast iron skillet, char the cut side of each onion half until well caramelized, about 3 minutes.
Combine all ingredients into a stockpot or kettle.
Bring to a boil, then reduce to a simmer.
Monitor the heat and continue to simmer for 60 minutes. Using a ladle, skim any scum that rises to the surface. DO NOT BOIL.
Remove from the heat. Cool slightly.
Carefully strain cooled broth through a fine mesh strainer lined with cheese cloth into a clean food storage container.
Cool completely.
Transfer to clean food storage containers. Cover, label, date and store refrigerated.
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