Wash, stem and slice peppers (leave seeds in). Put in a large pot.
Peel and chop the onion into quarters. Add to pot.
Wash the apples. Stem and quarter them, scrape out and discard the seeds, add to pot (no need to peel or fully core.) Add to pot.
Add vinegar to pot.
Peel garlic, mince, add to pot.
Add mustard seed, salt and turmeric to pot.
Crush the nutmeg into pieces (by using side of a chef's knife or other means) and add three-quarters of the pieces you get to the pot.
Stir pot, bring to a boil. Reduce heat to medium-low, cover and simmer for about an hour, stirring from time to time OR 30 minutes in a pressure cooker on high, natural release.
Press through fine disc of food mill, or a sieve.
Put in a pot and reheat to piping hot.
Ladle hot sauce into heated jars, leaving 2 cm (½ inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process jars for 15 minutes; increase time as needed for your altitude.