Blend both chilies, garlic, and water until it looks slushy but not smooth—stop blending as soon as you don't see any more big chunks.
Transfer into a heavy bottomed pot. Add sugar, vinegar and salt and stir to mix.
Bring the mixture to a simmer, stirring in the beginning just until all the sugar is dissolved. Let simmer for 5 minutes. Keep a wet pastry brush handy and if the sides of the pot starts to brown, brush it off with some water to prevent it from burning.
Once it is done simmering, add tapioca slurry while stirring, and keep stirring until it comes to a boil.
Remove from heat, taste and adjust seasoning as needed. Transfer into a jar and let cool. This will keep in the fridge for many months (I've yet to see it go bad!).
Serve with fried chicken, spring rolls, or any deep fried foods.
