1) Put the eggs in a saucepan with enough cold water to cover. Bring to the boil, cover, and remove from the heat. Set aside for 12 minutes. Drain the eggs and roll them between your palm and the counter to crack the shell, then peel under cool running water.
2) Dice the eggs and combine with mayonnaise and mustard. Season with salt and pepper. Stir in the spring onions, celery, and radish. Divide the egg salad among the lettuce leaves, top with the sprouts and roll.