Boil 180 millilitres of water and dissolve the palm sugar in it. Peel and finely chop or grate the shallots. Add to the water together with the chilli paste, tomato paste and vinegar.
bring to the boil. Mix starch with a little water until smooth and stir into the hot sauce. Bring to the boil again briefly and season to taste with soy sauce. Cut chilli pepper into rings, remove seeds and sprinkle on the sauce.