To make the hollandaise sauce, whisk the egg yolks in a bowl until creamy.
Place the lemon juice and vinegar in a small sauce pan along with the bay leaf and bring to the boil. Remove from the heat and pour slowly into the egg yolks in a steady stream, whisking continuously.
Pour the melted butter into the egg mixture in the same way, whisking continuously until the sauce has thickened.
Add a pinch of nutmeg and season to taste. Keep warm and stir at regular intervals to prevent a skin from forming.
Lightly toast the ciabattas on both sides, drizzle with olive oil and rub basil leaves into the bread. Lay a slice of Parma ham on top of each and then grill for 1-2 minutes. Keep warm.
To poach the whole eggs, bring a large saucepan with 10cm water to the boil. Crack each egg into a small bowl and then tip carefully into the boiling water. Poach for 2½ minutes and then carefully lift out of the water. Drain.
To serve, place a poached egg on top of each slice of ciabatta, spoon over plenty of the hollandaise sauce and arrange another slice of Parma ham on top of each serving.
Cook's tip: Poach 2 eggs per serving if you are feeling especially hungry. The nutmeg can be omitted if you prefer.
Public health advice is to avoid consumption of raw or lightly cooked eggs especially for those vulnerable to infection including pregnant woman, babies and the elderly.