Wash the stilts well and finely chop the lemongrass.
In a pot, bring plenty of salted water to a boil. Add the lemongrass, put in the stilts and boil vigorously once. Reduce heat and cook stilts, covered, until almost but not quite tender, at least 1 hour.
Meanwhile, coarsely chop the peanuts and mix with the spices. Stir in the sugar.
After about 1 hour of cooking, add this mixture to the stilts and continue cooking, uncovered, until the stilts are soft and the liquid has thickened considerably.
The sauce can be thickened with coconut milk if desired.
Serve the stilts on warmed plates and sprinkle with coarsely chopped coriander greens.