Blend: In a blender, combine the red jalapeño peppers, garlic cloves, brown sugar, and kosher salt. Blend until a smooth paste forms.

Ferment: Transfer the mixture to a clean jar, leaving a tiny bit of space at the top for expansion. Cover the jar tightly with a lid. Let the mixture ferment at room temperature, away from direct sunlight, for around 5 days. Check after 24-36 hours (24 if warm, 36 if cooler). There should be a little popping sound when you open the jar, indicating gas bubbles are present. Using a very clean spoon, stir once you see any fermentation bubbles. Close the lid and continue fermenting for 36-48 more hours, then check again. The fermentation can take anywhere between 5 days and 10 days, depending on room temperature.

Cook: After fermentation, transfer the mixture to a saucepan. Add the distilled white vinegar and bring to a boil. Lower the heat and simmer for 5 to 10 minutes, allowing the flavors to meld.

Blend again: Let the mixture cool slightly, then blend again until smooth. If the sauce is too thick, you can add water to reach your desired consistency.

Strain: Strain the sauce through a fine mesh strainer into a bowl, pressing to extract as much liquid as possible. Discard the solids.

Bottle and store: Transfer the strained sauce into a clean bottle or jar. Store in the refrigerator. The sauce will keep for up to 6 months, often becoming more flavourful as it ages.