Start by mincing the fresh ginger, hot chilli pepper, and garlic. This prep work is essential for infusing the sauce with authentic flavor.
Measure out the water, rice vinegar, sugar, and ketchup so you have everything ready for a smooth cooking process.
In a medium saucepan, combine the water and rice vinegar. Bring this mixture to a boil over medium heat.
Once boiling, add in the sugar, minced garlic, minced ginger, chopped chilli pepper, and ketchup. Stir well to combine all the ingredients.
Reduce the heat and let the mixture simmer for about 5 minutes. This will help dissolve the sugar and soften the garlic, allowing the flavors to meld beautifully.
While the sauce is simmering, prepare the cornstarch slurry. In a small bowl, mix the cornstarch with 2 tablespoons of water until smooth.
Whisk the cornstarch slurry into the simmering sauce. Stir continuously as the sauce heats.
Continue to stir until the sauce begins to thicken and clear. This should take about 2-3 minutes. The desired consistency is thick enough for dipping but still pourable for glazing.
Once thickened, remove the saucepan from the heat. Let the sweet chilli sauce cool slightly.
Transfer the sauce to a clean jar or bottle. It can be stored in the refrigerator for up to two weeks.