Melt 60g butter in a deep frying pan over a medium heat. Whisk in 80ml water and the mustard. Add the leeks, season, reduce the heat to low and cover. Cook undisturbed for 20-25 mins, or until the leeks are tender. Remove from the heat, stir through the parsley and capers, then cover to keep warm.

Bring a medium pan of water to a simmer, add the vinegar and swirl the water with a wooden spoon to create a whirlpool. Crack an egg into the centre of the whirlpool and poach for 3 mins. Carefully remove using a slotted spoon, then repeat with a second egg.

Beat the remaining eggs with the milk and half the parmesan. Season. Pour the mixture into a shallow bowl, then place each slice of bread in the liquid for 1 min to soak, turning once. Heat the remaining butter in a large non-stick frying pan with a small drizzle of oil and fry the soaked bread for 3 mins on each side, or until golden brown.

Top each pain perdu with confit leeks and any juices from the pan, a poached egg and a sprinkling of the remaining parmesan.