Start by adding the red chilies and water into a blender. Blend on high speed until the mixture becomes completely smooth and slightly thick. Make sure there are no large chili pieces left, as a smooth base will give your sauce that glossy, professional texture. If needed, pause and scrape down the sides to ensure everything blends evenly.

Carefully pour the blended chili mixture into a saucepan. Place it over low to medium heat—avoid high heat at this stage, as it can affect the balance of flavors and cause the mixture to cook too aggressively.

Add your sweetener, vinegar, minced garlic, grated ginger, salt, and fish sauce into the saucepan. Stir gently to combine everything. At this point, the sauce will start to smell rich and aromatic as the garlic and ginger release their flavors. Make sure all ingredients are evenly mixed so no part of the sauce tastes too strong or too mild.

Let the mixture simmer gently for about 5–10 minutes. Stir occasionally to prevent sticking at the bottom. You’ll notice the sauce slightly thickening and the flavors becoming more rounded. Keep the heat low to preserve the freshness of the ingredients and avoid overcooking, which can dull the taste.

In a small bowl, mix the cornstarch with water until it forms a smooth, lump-free slurry. Slowly pour this mixture into the saucepan while stirring continuously. This step is important—adding it gradually while stirring prevents clumps and ensures a smooth, even consistency.

Continue stirring the sauce over low heat as it thickens. Within a few minutes, you’ll see it turn glossy and slightly translucent. Keep stirring until you reach your desired thickness—remember, it will thicken a little more as it cools.

Once the sauce has thickened properly, remove the saucepan from heat. Allow it to cool at room temperature for about 10–15 minutes. This cooling stage helps the flavors settle and develop a more balanced taste.

Transfer the cooled sauce into a clean, dry glass jar. Seal it tightly and store it in the refrigerator. Before each use, give it a quick stir or shake, as natural separation can occur. The sauce will stay fresh and flavorful for several days when properly stored.