Ravioli of Leeks and Truffles

This is one of the most perfect pasta dishes I know. It is assumed that you have already made pasta (the recipe for which is) and there is no point in trying to make this without a pasta machine.

Black truffles are expensive but a little goes a long way in this recipe and you will have made enough truffle butter to freeze for another day (truffles freeze extremely well). Truffle butter also keeps in the freezer and makes