Remove chilies from pan and place in blender, reserving liquid. Taste liquid, if it is bitter, use plain water. Place enough water or cooking liquid to cover chilies. Place a kitchen towel on lid and hold down to prevent steam from escaping- Pulse blender off and on, then puree chilies; add more water if necessary .Remove chili sauce from blender and strain through fine sieve or cheese cloth into a clean container. The pure chili sauce should be the constancy of ketchup.