What is "Jansson's temptation"?

Janssons frestelse is made with anchovies instead of pickled sprats in many of Sweden's provinces such as Varmland. It is an absolute must for Christmas dinner or Julbord. And it is a temptation! I could eat an entire casserole by myself! But alas, I must share with my dinner guests.

I have made a similar dish made with pickled cabbage (saurkraut). It's yummy

It was great to see von Trier's name.