If you're making the curry paste in a mortar and pestle, start by smashing the lemongrass, and add each ingredient from there. If you're using a food processor or blender, combine the lemongrass, garlic, shallots, chiles, ginger, cumin, and turmeric, and pulse until the ingredients start to come together.
You can add the oil at this point, and blend again. Stir in the lime oil or zest. The paste will keep in the refrigerator for about a week. Freeze any paste you wont use for future use.
Makes about 1 cup.