Wow! I served this to a dinner party of 10 and it was a huge hit - everyone wanted the recipe. It will become a permanent part my repertoire. Six large leeks made a lot more topping than in the photograph - mine was totally covered with a thick layer of leeks.-but it was wonderful ( I will use a bit less next time!) . Two medium baking potatoes would have worked - I had more potatoes than needed. I did use 1/2 whole wheat flour and the truffle oil. Delicious recipe!