Bring a large pot of water to a boil over high heat.
While water comes to a boil, score an “X” on the bottom of the peaches with a paring knife. Prepare a large bowl with an ice bath.
When water is at a full boil, add peaches. Boil for 30 seconds.
Immediately transfer the peaches to the ice bath and peel the skins off of the peaches.
Remove the pit from the peaches and roughly chop. Add to a large bowl with sugar, brown sugar, lemon juice, chilis and salt. Toss in the ½ lemon as well after juicing.
Mix to combine and let the mixture sit for at least one hour, or refrigerate overnight to really let the flavors infuse.
Transfer mixture to a medium pot and turn heat to medium low. Cook stirring often, to prevent scorching, while also mashing up the peaches to your desired consistency.
Continue to cook and stir, until peaches are broken down, the mixture is thick and jammy and reaches between 217-220F on an instant read thermometer. This should take about 30-40 minutes.
Let mixture cool, then store in an airtight container. This will keep in the fridge for up to 6 months! It's great on toast, used in a cocktail, on a sandwich, the possibilities are endless :)