This recipe is very simple and is quite delicious, especially if you can find whole fermented soybeans. You can also embellish it with garlic, chilies, and ginger and serve it on grilled fish, chicken, and beef. If you can't find soybeans, substitute 1/3 cup of hoisin sauce and omit the sugar.
- Place the soybeans (or hoisin sauce), water, coconut milk, vinegar, onions, and sugar in a blender or food processor. Process just until the mixture is smooth.
- Transfer to a saucepan and bring to a boil over moderate heat. (If you don't have a food processor or blender, cook the soybean mixture first, then beat with a whisk.) Reduce the heat and simmer until the sauce thickens enough to coat a spoon, about 5 minutes. Add a little water if it's too thick. Set aside to cool.
- To serve, transfer to individual sauce bowls and garnish with chili paste and chopped peanuts. Sauce will keep up to two weeks if refrigerated.