Janssons frestelse, also known as Jansson's temptation, is a creamy potato casserole traditionally served at Christmastime in Sweden. (This dish is also served in Finland, where it’s known as janssoninkiusaus.) 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. This fish has actually caused quite a bit of confusion in recipe translations: “It’s worth seeking out the right kind of sprats, such as Abba Grebbestad tinned sprats—confusingly they are known in Swedish as ‘ansjovis,’ which is logically translated as anchovies in English,” writes Signe Johansen in Smörgåsbord: Deliciously Simple Modern Scandinavian Recipes. “The spice-cured sprats, however, are less salty than anchovies and give a more distinctly Swedish flavor to this modest dish.”
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.
- Prep time 10 minutes
- Cook time 1 hour 15 minutes
- makes 1 casserole
unsalted butter, divided
large yellow onion, halved through the root end and thinly sliced
garlic cloves, thinly sliced
Freshly ground black pepper
2 to 2½ pounds
potatoes (about 3 or 4 large russets or about 6 large Yukon Golds), scrubbed
4 to 5 ounces
tinned spice-cured sprats (or 2 ounces oil-packed anchovies), drained and roughly torn, oil reserved
cinnamon (optional, if using anchovies)
nutmeg (optional, if using anchovies)
- Heat the oven to 425°4F. Rub 1 tablespoon of the butter around a 9- to 10-inch deep-dish pie plate or a 2-quart casserole dish.
- Heat 3 tablespoons of the butter in a skillet over medium-low heat. Add the onion and sliced garlic, season with salt and pepper, and sauté, stirring regularly, until softened but not browned, about 5 to 7 minutes. Remove from the heat.
- Thinly slice the potatoes into ¼-inch-thick matchsticks. Layer a third of the potatoes into the pie plate and season with salt and lots of black pepper. Add half the onions, then scatter over half of the sprats or anchovies. Layer another third of the potatoes, season, then add the remaining onions and anchovies. Add the remaining potatoes and season once more.
- Pour the milk and cream into a small bowl or liquid measuring cup and stir in the cayenne (and cinnamon and nutmeg, if using). Pour this mixture over the casserole (it should come up about three-quarters of the way).
- Top the casserole with the panko. Season with salt and pepper, then dot the remaining butter over the surface. Cover the pie plate tightly with foil.
- Bake the casserole for 45 minutes, then remove the foil and bake for another 15 to 20 minutes, until golden brown and bubbling. Let cool slightly, then serve.