Blend the Base: In a blender or food processor, combine the red bell pepper, bird’s eye chilies, onion, and garlic. Pulse until the mixture is finely blended but not completely smooth for a slightly chunky texture.

Cook the Sauce: Pour the blended mixture into a saucepan and add the water, vinegar, salt, and sugar. Cook for 10-15 minutes, stirring occasionally, until the peppers and onions soften and the flavors meld together.

Thicken the Sauce: In a small bowl, mix the potato starch or corn starch with 2 tablespoons of water to create a slurry. Slowly add the slurry to the simmering sauce, stirring constantly to prevent lumps. Continue to cook for another 2-3 minutes, or until the sauce thickens to your desired consistency.

Cool and Store: Remove the sauce from the heat and let it cool slightly. Pour the mixture into a clean, airtight jar or container. Keep it refrigerated, where it will stay fresh for up to 2 weeks.