The ingrediens are roasted or grilled until charred, concentrating the flavors rsulting in a very hot sauce.
- Broil / grill the garlic, chilies, shallots, and tomato under high heat, turning once, until soft and slightly charred - for about 20-30 minutes. Allow them to cool.
- Remove seeds from the chili peppers and tomato, squeeze the roasted garlic out of the skin, and tranfer everything to a mortar and pount into a paste with the pestle.
- Mix in sugar, lime juice and fish sauce; and the oil, if using.
- Garnish with chopped coriander.
Some recipes use grilled eggplant instead of tomato, or a combination of eggplant and tomato. That is fine. You can also substitute shallots with half the amount of banana shallots, or a quarter of the amount of white onion - onion will have a stronger taste.
Thai chilies are very hot. You can substitute half of them with a milder variety of green chili, to control heat without compromising flavor. Adding vegetable oil also affects the strength of the result.
If you don't want to use the grill or oven, the ingredients can be cooked in a skillet, stirring continuously, preferably with little or no oil.