Preheat oven to 190C/375F/Gas Mark 5.
First prepare the pastry: Sift the flour into a glass bowl and add the cubed butter, incorporating the flour and butter until it resembles breadcrumbs. Add the Parmesan cheese and stir through.
Create a well in the centre of the mixture and add the egg yolk and water, and work until the dough comes together. Cover with cling film, place in the fridge for at least half an hour.
Turn out onto a lightly floured surface Divide the pastry into 10–12 equal pieces and roll each piece of pastry in 5mm depth.
Grease 10–12 tartlet cases and press each pastry disc into place. Place on a baking tray and fill with baking ceramic beans. Place in the fridge for half an hour to rest.
Bake blind in the oven for 15 – 18 minutes until cooked.
In the meantime, combine the garlic and O’Hellmann’s in a bowl. Add the prawns and allow to marinade in the flavoured mayonnaise. Preheat a griddle pan and add a little olive oil. Skewer 3-4 prawns onto wooden or metal skewers and lay on the griddle pan. Cook for 1–2 minutes on each side, then remove from the pan and keep warm.
In the same pan add the leek and shallots and cook over a medium heat for 3-5 minutes until softened.
Add the white wine, and cream and cook for a further 4–5 minutes until reduced and coats the back of a spoon. Season with salt and pepper.
Divide the leek mixture between each pastry case and top with 3–4 prawns. Add the Parmesan and place under a hot grill for a minute or two to melt the parmesan.
Dress with some cherry tomatoes and baby green leaves and some O’Hellmann’s.