Combine the tamarind, sweetener, fish sauce, curry paste, and water in a medium saucepan. Cook over a medium heat until the sweetener has fully dissolved.

To thicken the sauce, sprinkle a little xanthan gum over. I recommend starting with about an eighth of a teaspoon, and gradually adding more until you get the thickness that you like. 

Let the sauce cool, then store in the fridge for up to three days.

To serve, sprinkle with a few toasted sesame seeds.