Heat a skillet to medium heat. Toast coriander, white pepper and cumin for 3 - 4 minutes until fragrant.
Place the toasted coriander, white pepper and cumin in a mortar and grind into a paste.
Add chilies on top and grind again into a paste, about 5 - 10 minutes. Add salt to taste, about ¼ teaspoon. If the mixture is too dry add a bit of water, a few drops at a time.
Next, rough chop the garlic and shallots. Add the garlic, shallots, lemongrass, cilantro stems, lime zest and (optional) galangal and grind again into a paste. You may need to grind your ingredients for 10 minutes or so.
Finally, once your mixture looks like tomato paste, add some shrimp paste, a little bit at a time, to taste. Store your red curry for up to two weeks in the refrigerator.