Step 1

Remove about half the seeds from the red chilies and bird’s eye chilies to moderate the heat. Add the chilies and garlic to a food processor and pulse until coarsely chopped.

Step 2

In a small saucepan over medium heat, combine the sugar, rice vinegar, water, fish sauce, and salt. Stir well and bring the mixture to a gentle simmer until the sugar has fully dissolved.

Step 3

Stir in the chili-garlic mixture and continue to simmer for about 5 minutes, stirring occasionally, until the sauce slightly reduces and the flavors meld.

Step 4

Mix the cornstarch with water to create a slurry, then add it to the saucepan. Stir immediately and cook for another 30 seconds until the sauce thickens to a syrup-like consistency.

Step 5

Remove the pan from heat and allow the sauce to cool completely. It will continue to thicken slightly as it cools. Transfer to an airtight jar and refrigerate for up to 2 weeks.