Peel course outer layer from lemon grass, and remove tough tops. (Save these for a soup stock if desired). Chop tender stalks into 1 inch lengths. Place in workbowl of food processor with shallots, garlic, coriander, hot chili sauce, cumin seeds and turmeric. Whirl to a fine paste, adding water if needed. In a large frying pan over medium setting , heat oil, add lemon grass paste and dried shrimp paste, stirring and frying for about 4 minutes or until mixture emits a wonderously aromatic perfume. Stir in about half the coconut milk and continue cooking, stirring almost constantly, for 8 minutes. Stir in remianing coconut milk, sweeten with sugar and season with salt. Blend in peanuts. Taste at this point to adjust sweetening, salt, and hotness. Thin with more coconut milk or water if desire.