Soak the tamarind pulp in boiling water and leave as you prepare peanuts and other ingredients.
If you have not already cooked the shallots and shrimp crackers, I recommend doing those first before you make the salad. Add a layer of neutral oil, such as canola or sunflower oil, to a small skillet/frying pan over a medium heat. Follow instructions on packet but watch as the crackers cook very quickly.
Roughly chop the garlic and chili, if using. I recommend briefly frying the peanuts, if you use roasted peanuts, to add more flavor. Cook until gently starting to brown then drain as you remove them with a straining spoon and drain on paper towel. If you use ready-fried then this is not needed. Fry the garlic and chili for a minute or two until soft then remove and drain.
Place the peanuts, softened garlic and chili in a small food processor or blender. Blend until well chopped and blended - if can be a little chunky or smooth, as you prefer (and some will depend on your machine).
Squeeze the tamarind pulp to try to extract as much flavor from and juices from it as you can - the liquid should become thicker. Strain the mixture to hold back the chunks of pulp but try to push through as much of the liquid as you can.
Add the other sauce ingredients except water to the ground peanuts - kecap manis, palm sugar, salt, tamarind, lime juice. Blend to mix. Add some warm water, just part at first if you want to get a consistency that works. It should be pourable but not too thin. Remember it will thicken a little as it cools. Set aside.