In a wooden salad bowl, add lemon or lime juice, and finely grate in egg yolk (using the fine side of a box grater or a zesting rasp). Stir in garlic, mustard and anchovy paste (if using) with a fork. Stir in olive oil in a thin stream, then stir in water, Parmesan and season to taste.
Add lettuce, bacon, croutons and reserved chopped egg white and toss. Serve salad garnished with Parmesan curls (peeled from cheese wedge using a vegetable peeler).
For added flavour, toast croutons in the pan used for cooking your bacon. Simply sauté cubes of day-old bread in the bacon fat and season with pepper (usually the bacon fat adds enough salt).