Place the potatoes in a saucepan of boiling water and cook for 12–15 minutes until tender. Drain, lightly crush with a fork, then stir through the spring onions, crème fraîche and watercress and season well with pepper. Keep warm.
Put the fish and milk in a large frying pan with the bay leaf. Bring to the boil, then cover and simmer for 5–6 minutes until the fish is cooked through.
Meanwhile, bring a saucepan of water to the boil, swirl the water with a spoon and crack in an egg, allowing the white to wrap around the yolk. Simmer for 3 minutes, then remove and keep warm. Repeat with the remaining eggs.
Serve the haddock on top of the potatoes, topped with the poached eggs.