Form 4 "nests" from foil to hold eggs upright. Place in a steaming basket. Cook eggs in pan of gently boiling water for 1 1/2 minutes; remove.
Carefully peel a small part of pointed end of eggs. With the point of a slim, sharp knife, cut a small hole down through the exposed white of each egg; reserve pieces of white that are removed. Pore liquid egg yolk and white from egg into a small bowl. Thoroughly mix in pork, prawns, fish sauce, garlic, coriander and pepper. Carefully spoon into eggs and replace removed pieces of white.
Set steaming basket over a saucepan of boiling water and place eggs, cut end upper most, in foil 'nests'. Cover basket and steam eggs for about 12 minutes. When cool enough to handle, carefully peel off shells. Serve whole or halved on lettuce leaves, garnished with coriander springs.