First, ferment the chili peppers. Process your fresh peppers in a food processor. If you don’t have a processor, use a mortar and pestle or simply finely chop them. Pack them into a jar, leaving at least 1 inch of head space. The peppers may rise a bit when fermenting.
Next, mix 1 quart unchlorinated water with 3 tablespoons sea salt. Pour just enough brine over the peppers to cover them, pressing them down a bit as you go. It is important to keep the peppers covered with brine to avoid spoilage. Check this daily.
Screw on the lid and set the jar away from direct sunlight to ferment for at least 1 week. Ideal temperatures are between 55-75 degrees F. The most active fermentation period is between 1-2 weeks, so be sure to monitor it during this time. “Burp” the jars often by unscrewing the lid a bit to let out some of the accumulating gases - watch out for splatter. Or, use an airlock or membrane for easier fermenting. The peppers must be submerged beneath the water to avoid mold growth. If the peppers aren't submerged, they might not ferment properly.
After 1-2 weeks, the fermenting activity will diminish and the brine will turn cloudy and taste acidic.
Strain the fermented peppers but retain the brine. Add the peppers to a large pot along with garlic, brown sugar, granulated sugar and vinegar. Add 1 cup of the brine PLUS 1/2-3 cups fresh water, depending on desired thickness (see Notes). Bring to a boil. Reduce heat and simmer for 5-10 minutes to let the flavors meld.
Cool slightly then add to a food processor or blender and process until smooth.
Strain the mixture through a fine mesh strainer to remove the solids, if desired. Pour into hot sauce bottles and enjoy.