First make the pastry. Rub butter, flour, Parmesan and salt together in a mixing bowl until the mixture has the consistency of fine breadcrumbs. Add the egg and bring it all together into a dough. Knead lightly. Cover in cling film and refrigerate for an hour before use.
Meanwhile poach the haddock. Place in a shallow pan and cover with milk. Slowly bring to a simmer until the fish is just cooked and starting to flake (about 5 mins). Drain and allow to cool.
Preheat the oven to 200˚C
Roll the pastry out to 3mm (1/8 in) thick and use to line 2 greased individual tartlet moulds. Place in the fridge to rest again then fill with greaseproof paper and baking beans and bake blind for 11 minutes.
Remove the beans and paper and cook for a further 8-9 minutes, until golden. Remove from the oven and allow to cool.
Reduce the oven temperature to 180˚C
Whisk the eggs and cream together. Heat the olive oil in a pan and sauté the leeks and spring onions until softened, but not coloured. Season with salt, pepper and cayenne. Allow the leek mix to cool slightly and then fold into the egg mix. Stir in the Parmesan and the flaked haddock. Divide between the cooled pastry tarts and place in the oven for approximately 20 minutes, until just firm. Serve with leaves and tomato salsa.
These can be made in advance and heated through for 10 minutes in a warm oven and are perfect for a special Mother's Day treat.