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Roast the peppers to remove skin; quarter lengthwise and devein. Set aside.
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Combine the apricots, plums, three cups of vinegar and water in a large non-reactive kettle and simmer until soft; about 25 minutes.
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Remove from heat and set aside.
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In another non-reactive kettle, this one very large, combine the remaining vinegar, sugars, and Karo and bring to a boil, stirring.
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Add the fruit mixture, ginger, salt, mustard seeds, onion, chiles, garlic, cinnamon, and the skinned bell peppers.
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Simmer, covered, for five minutes then simmer uncovered for one hour, stirring every so often.
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Remove the cinnamon stick.
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With a food processor, pulse the mixture for a couple of seconds (this has to be done in batches; * process a little longer if you like a less-textured sauce).
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Return to the kettle and boil gently, stirring, until the sauce has thickened, about 15 minutes (the sauce will thicken some more as it cools).
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Ladle into sterilized jars, either half-pint or pint.
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Process in a boiling water bath for 10 minutes (for half-pint jars) or 15 minutes (for pint jars).
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Allow to age in the jar for 2 to 4 weeks before using.