Chop jalapeños in a food processor using the pulse setting. (I use three jalapeños without seeds and two with.).
In a large pot, place washed peaches and use a potato masher to crush. I don’t peel or pit the peaches.
Add vinegar and jalapeno peppers. Bring to a boil over high heat. Reduce heat and simmer, covered for about 20 minutes or until peaches and peppers are very soft.
Using a colander lined with several layers of cheesecloth, strain the mixture for at least 2 hours and discard the solids. (I line my colander with three J cloths to cover the holes) There should be about 2 cups of liquid.
In a large pot, combine the 2 cups of strained liquid and the sugar. Bring to a full rolling boil over high heat, stirring constantly.
Quickly stir in pectin then return to a full rolling boil. Boil hard for 1 minute, stirring constantly.
Remove from heat. Skim off foam with a metal spoon.
Ladle hot jelly into hot half-pint jars, leaving a ¼-inch headspace. Jars need to be hot so that the hot jelly doesn’t break the glass. .
Wipe jar rims with a wet paper towel then place metal lid on top.
Screw metal ring until just starting to resist. Don’t over tighten.
Process filled jars in a boiling water canner for 10 minutes. .
Remove jars from canner and cool on wire racks. Before serving, let jelly stand at room temperature for until jelly is set. It may take 2 to 3 days for jelly to set so don’t panic if it doesn’t set right away. .