Bring a deep saucepan of water to the boil (at least 2 litres) and add 3 tbsp white wine vinegar. Break the eggs into 4 separate coffee cups or ramekins. Split the muffins, toast them and warm some plates.
Swirl the vinegared water briskly to form a vortex and slide in an egg. It will curl round and set to a neat round shape. Cook for 2-3 mins, then remove with a slotted spoon.
Repeat with the other eggs, one at a time, re-swirling the water as you slide in the eggs. Spread some sauce on each muffin, scrunch a slice of ham on top, then top with an egg. Spoon over the remaining hollandaise and serve at once.