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1
Preheat the oven to 350 u00b0 F. Place the onion and ginger on a rimmed baking sheet and roast until the onion is soft and beginning to ooze, about 1 hour. Remove from the oven and let the onion and ginger cool until they can be handled. Peel the onion and cut in half. Slice the unpeeled ginger into 1/4-inch-thick coins.
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2
While the onion and ginger are roasting, blanch the bones: To ensure the pot is large enough to blanch the bones without boiling over, put the bones in the pot and add water to cover by 1 inch. Then remove the bones and bring the water to a boil. When it is at a rolling boil, add the oxtails, neck bones, and shanks. Return the water to a boil and boil for 3 minutes. Drain the contents of the pot into a colander and rinse under cold running water. Rinse the pot and return the rinsed oxtails, neck bones, and shanks to the pot. Add the marrowbones.
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3
Add the onion halves, ginger slices, sugar, salt, and 8 quarts fresh water to the pot and bring to a boil over high heat, skimming off any scum that forms on the surface. Lower the heat so the liquid is at a gentle simmer and simmer for 4 hours, skimming as needed to remove any scum that forms on the surface.
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4
Add the pepper, cinnamon, star anise, clove, and cardamom and continue cooking, skimming occasionally, for 1 hour longer.
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5
Remove from the heat and and, using a spider or a slotted spoon, discard the large solids. Strain the stock through a fine-mesh sieve into a large container, let sit for a few minutes (or refrigerate overnight), then skim most of the fat from the surface (leave some, as it gives the stock a better flavor and mouthfeel). Use immediately, or let cool completely, then transfer to practical-size airtight containers and refrigerate for up to 3 days or freeze for up to 3 months.
