Place the tamarind in a bowl and mash it to extract the tamarind concentrate.

Heat a pan over medium heat, add a little cooking oil, then sauté the chopped onion and minced garlic until fragrant. Add the tamarind concentrate to the pan.

Next, add the sugar, fish sauce, chili sauce, and satay chili oil. Stir well and cook until the mixture thickens.

Taste and adjust the seasoning as needed, then turn off the heat.

Pour the tamarind dipping sauce into a bowl, add sliced fresh chili and crushed roasted peanuts, stir well, and serve as a dip for rice paper.