To prepare the leek, slice it almost in half lengthways, then fan it out under a running tap to wash away any trapped dirt.
Now slice each half into four lengthways, then into ¼ inch (5 mm) slices. After that, put the Boursin into a medium-sized bowl and cut the potatoes in half lengthways. Protecting your hands with a cloth, scoop out the centres of the potatoes into the bowl containing the Boursin, add the milk or cream and season well with salt and freshly milled black pepper. Now quickly mash or whisk everything together, then pile the whole lot back into the potato skins.
Now scatter the leeks on top, followed by the grated Cheddar – pressing it down lightly with your hand – then place on the baking sheet and bake in the oven for 20 minutes or until the leeks are golden brown at the edges and the cheese is bubbling
Pre-heat the oven to gas mark 4, 350°F (180°C).
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