Peel all garlic and remove any green stems in the middle (cut each clove length-wise in order to see if there's any green).

Add garlic and sea salt to your food processor, then pulse them for 30 seconds in five-second intervals, until well-balanced and fully minced. You'll want to scrape down the sides halfway through.

Add 2 teaspoons of oil to the garlic mixture, ideally while the food processor is running (or if needed then all at once and immediately run the food processor and whip), then scrape down the sides.

Add another teaspoon or two of oil one at a time, ideally while the processor is running, and emulsify everything for 10 more seconds.

Alternate adding a half tablespoon of the mustard powder or a tablespoon of the oil, alternating adding the sumac once the ground mustard has all been added. If you add the powders or the oil too quickly, it can break the emulsification, so carefully blend the mixture well between additions. If the emulsification isn't too thick at the end, you may not need to add the final tablespoon of oil, so add everything slowly. Once everything has been added, your sauce is done!