Roughly chop the Hatch chilies and jalapeños. Toss them into a clean 1-gallon fermentation jar along with the chopped onions and peeled garlic cloves.

Make a 3% brine using non-iodized salt (like pink Himalayan). Pour the brine over the ingredients until fully submerged. Use a brine-filled baggie as a weight to keep everything below the surface for anaerobic fermentation.

Seal the jar with an airlock lid and place it in a dark cabinet. Let it ferment for 3 months. Expect the colors to deepen, textures to soften, and a tangy aroma to develop.

After 3 months, remove the vegetables with a slotted spoon and add them to a pot or blender. Add about 2 cups of the brine and blend until smooth. Optionally, add vinegar for acidity and thin the consistency. Taste and adjust with more brine or vinegar as needed.

If the sauce is too thick, strain half or more through a fine mesh strainer. This helps create a smooth, pourable texture perfect for dropper bottles.

Pasteurize the sauce on the stove for 10–15 minutes. Ladle it into sanitized bottles using a funnel. Cap with droppers and apply shrink tops if gifting. Use the hot-fill flip method for safe sealing.