Step 1: Prick both potatoes all over with a fork. Rub in vegetable oil and salt (this will make the skins nice and crispy). Bake in the oven at a reasonably high temp (about 200 C) for about 1hr 30mins. Take out the baked potatoes and cut them in half. Scrape out the cooked potato inards, making sure to keep the skins intact. Mash the potato in a bowl with some boursin to taste, and then put this mixture back in the potato skins. sprinkle the sliced leek on top of each open potato half, followed by the cheddar. Return to the oven for 15-30 mins to brown. Voila, you have a tasty meal, which may impress your flatmates!