An easy, simple salad with a slightly unusual dressing that's a classic in Laos.
Start by hard boiling the eggs. You can use your preferred method, but probably the easiest is to put the eggs in a pan, cover with cold water at least 1in/2.5cm over the eggs and bring to the boil. Once the water boils, turn off and leave the eggs in the water for 10-12min then drain and run under cold water to stop them cooking. When cool, carefully peel the eggs.
As the eggs are cooking, roughly chop the lettuce (and other greens, if using) and divide between 2-3 plates, along with the watercress.
Slice the tomato and cucumber and lay on top of the greens.
Scatter over the peanuts, if using, and cilantro.
Cut two of the eggs in half and remove the yolk. Mash or break up these two yolks in a small blender. Add the remaining dressing ingredients (oil, lime juice, vinegar, sugar and a little salt and pepper) and blend until smooth. Note make sure the yolk is broken up and smooth before you add the other ingredients or it won't work after.
Cut the remaining egg into quarters or slices and put on the salads. Cut up the leftover whites and add to the salads too, if you like. Drizzle over the dressing and serve.