First make sauce. Gently fry garlic and chilli in peanut oil until garlic is fragrant.
Add sugar and kaffir leaves and stir for 30 seconds, then add peanut butter and continue stirring until peanut butter softens and warms up.
Gradually add coconut milk then water, stirring well to combine. Continue stirring and allow mixture to simmer for 5 minutes. Sauce will darken and may split. Remove from heat, add the juice of 1 lemon or lime, then taste and add more if you like. Season with salt or fish sauce to taste.Discard surface oil if you like. Cover sauce and keep warm until serving.
Bring a saucepan of water to the boil. Salt the water well then gently add the eggs. Boil for 4 minutes then drain and set under cold running water for 1 minute. Carefully peel eggs.
Steam beans over boiling water for 3 minutes until just cooked. Cool briefly under cold running water then drain well.
Fry onion in vegetable oil over high heat until well browned and slightly crispy. Transfer onion on to paper towels.
Pile steamed rice in the centre of a warmed serving platter. Arrange beans, onion and cucumber on rice.
Cut eggs in half (centres will be runny) and quickly place on vegetables. Scatter coriander on top.
Quickly reheat sauce and transfer to a warmed bowl for offering alongside the gado gado.