Mines nothing fancy...
I generally just boil a potato along with some diced onion (as in, boil both together). Once boiled and drained, throw a mixture of various types of cheese in there and mix. You do need some mature or vintage cheddar in there so the taste stands out. Throw some mustard powder, salt and white pepper in there.
Load it all in to a pie, puff pastry of course.
Nom.