Even in Sumatra the region is important, indeed. But the region (Riau ) my family comes from is coconut central. so I assumed it was so for Sumatra as a whole as I often read Sumatra is the epicenter of coconut foods in Indonesia ( well and some the hottest food there too). My ancestry is a bit further down the line than yours though, my great grandfather was Indonesian and I have not been there myself. So correct me if I am wrong.My dad was born on Sumatra, but grew up on java during WW2
He taught me to cook.
The country is huge and of course, like everywhere, people adjust the recipes to their personal taste (and availability of ingredients).
Trassi? I'm unfamiliar with this.My recipe is as follows:
Ingredients for about 500 ml:
3 tablespoons of smooth unsweetened peanut butter (salted is OK)
50 grams of santen (creamed coconut) or half a block
250 ml milk or coconut milk, sometimes more
Ketjap manis (sweet soy sauce) at least one table spoon
Sambal badjak (fried onion sambal) at least one table spoon
1/2 teaspoon of trassi
1/2 teaspoon of fresh grated ginger
1/2 teaspoon of fresh grated garlic
Lemon or lime juice, one half lemon or lime
A spoonful of oil.
This is super easy. Get a saucepan, put all the ingredients except milk and lemon juice in and put it on low heat. Stir until the santen and peanut butter starts to melt. Add the milk while stirring so the other ingredients don't burn. When all the milk is added and it's been cooking for a while you should have a smooth, thick sauce that coats your spoon. If not, add some more milk. Then when it's right add a little lemon juice to make it slightly thinner and add contrast to the flavor. If nothing is burned, you're ready to eat!
Trassi, or terasi is simply a regional variation on shrimp paste. Most larger stores stock some form of shrimp paste - some other names are kapi, belacan and mam tom. The various varieties are all fairly similar, so there isn’t really a need to seek out or buy multiple versions, in my opinion.
Good Asian grocers will usually have a few different varieties and brands, but I generally use Prawn and Coral brand. A block will last a long time, even though you will use it so often.