Janssons frestelse, also known as Jansson's temptation, is a creamy potato casserole traditionally served at Christmastime in Sweden. It typically appears on the julbord, aka the Christmas smorgasbord, a multicourse buffet of myriad treats—among the pickled, cold, and hot fish; sliced meats, cheese, and desserts, Janssons frestelse gets served along with warm sides and meats toward the end of the meal.
Similar to a potato gratin, Janssons frestelse is quite simple: potatoes, onions, cream, and bread crumbs, plus one star ingredient you’d be less likely to find in a classic potato casserole: tinned fish. Technically, the dish calls for spice-cured sprats, which are small, oily fish similar in flavor and texture to anchovies or sardines.
Having tested with both, I’d say if you can find sprats, specifically Abba Grebbestad brand, you should most certainly use them here; but regular ol’ oil-packed anchovies make for an equally flavorful alternative. If you do decide to use anchovies instead of sprats, try adding a pinch each of cinnamon and nutmeg along with the cream—that subtle aroma from the wam spices will channel the flavors of sprat brine.
Please tell me it's herring.