The mango cubes and scallions are my personal additions. The tamarind sauce will be just as good without them but they do give the sauce additional flavor and visual appeal.Use as a dipping sauce or spoon over fried fish to make pla rad prik. Or toss with fried eggplants for a side dish.
With a mortar and pestle (or a blender or food processor), process the garlic, shallots (or onion), lemongrass and chilies to a paste.
Heat two tablespoons of cooking oil in a small frying pan.
Over medium heat, gently cook the paste with the fish sauce, sugar and tamarind paste until the solids separate from the oil. It’ll take about ten minutes with occasional stirring.
Add the bell peppers, cook for another 30 seconds, taste, and adjust the seasonings if needed.
Off the heat, stir in the mangoes and scallions, if using.