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Janssons frestelse, a classic Swedish potato casserole with a golden breadcrumb crust, baked in an oval cream ceramic dish with a wooden spoon and beige linen on a light wooden table.
Erik Lundström

Jansson’s Temptation – The Swedish Potato Gratin That’s Hard to Resist

Jansson’s Temptation is a classic Swedish potato gratin made with matchstick potatoes, sweet onions, and Nordic sugar-salted, spiced sprats baked in cream until bubbly and golden. It’s cosy enough for the Christmas julbord, but simple and hearty enough to serve as an easy weekday lunch with a crisp salad and rye bread.
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Prep Time 25 minutes
Cook Time 50 minutes
Total Time 1 hour 15 minutes
Servings: 4 people
Course: Dinner / Main Course
Cuisine: Finnish, Swedish
Calories: 420
Ingredients Method Notes

Ingredients
  

  • 2½ lbs starchy potatoes (like russet or Yukon Gold)– peeled and cut into thin matchsticks (about ¼ inch / 0.5 cm thick)
  • 2 medium yellow onions, thinly sliced
  • 5 tbsp unsalted butter
  • 2 x 3.5 oz cans Swedish spiced sprats– look for ansjovis–style sprats in a sweet, spiced brine, not Mediterranean anchovies in oil.
  • 2 cups heavy cream
  • ½ cup whole milk
  • ½–¾ tsp kosher salt, or to taste (go light; the fish and brine are salty)
  • ½ tsp white or black pepper
  • ½ cup plain dry breadcrumbs (panko or regular)
Optional but recommended:
  • 1–2 tbsp sprat brine (from the can) for extra flavor
  • A little butter for greasing the dish

Method
 

Preheat the oven
  1. Preheat your oven to 400°F (200°C).
  2. Lightly butter a 9×13-inch (about 23×33 cm) baking dish.
Prep the potatoes
  1. Peel the potatoes and cut them into thin matchsticks, about ¼ inch (0.5 cm) thick.
  2. If you work slowly, you can keep them in a bowl of cold water to stop browning—but dry them very well in a clean kitchen towel before layering, or the gratin will be watery.
Cook the onions
  1. In a large skillet, melt 3 tablespoons butter over medium heat.
  2. Add the sliced onions and a small pinch of salt.
  3. Cook 8–10 minutes, stirring now and then, until soft and sweet but not browned.
  4. Take off the heat and set aside.
Prep the sprats
  1. Open the cans of Swedish spiced sprats.
  2. Lift out the fillets and cut them into rough pieces or strips.
  3. Reserve 1–2 tablespoons of the brine from the can.
Mix the cream
  1. In a pitcher or bowl, whisk together:
    2 cups heavy cream
    ½ cup whole milk
    ½ teaspoon pepper
    A small pinch of salt (you can adjust later)
    1–2 tablespoons sprat brine for that classic sweet-salty seasoning.
Layer the casserole
  1. Spread ⅓ of the potatoes in an even layer in the dish.
  2. Top with ½ of the onions and ½ of the sprat pieces.
  3. Add another ⅓ of the potatoes, then the remaining onions and sprats.
  4. Finish with the last ⅓ of the potatoes on top.
  5. Pour the cream mixture evenly over everything—press down gently with a spoon so the cream seeps in.
Butter & breadcrumbs
  1. Melt the remaining 2 tablespoons butter.
  2. Sprinkle the top with ½ cup breadcrumbs, then drizzle the melted butter over the crumbs.
Bake
  1. Bake at 400°F (200°C) for 20 minutes, then reduce the heat to 350°F (175°C) and continue baking for another 25–30 minutes, or until:
    The potatoes are completely tender when pierced with a knife.
    The top is deep golden and crisp, and the cream is bubbly around the edges.
  2. If the top browns too fast, you can tent loosely with foil for the last 10–15 minutes.
Rest & serve
  1. Let the casserole rest 10–15 minutes before serving so it can set slightly.
  2. Serve warm with crispbread or rye bread, a simple green salad, and maybe pickled beets or quick pickled cucumbers on the side.

Notes

In Sweden, Jansson’s Temptation is made with sugar-salted, spiced sprats (Sprattus sprattus), sold as ansjovis in a sweet, aromatic brine – not with Mediterranean anchovies (Engraulis encrasicolus) packed in oil. If you’re in the US, look for “Swedish anchovies” or ansjovis in Scandinavian shops, IKEA’s food market, or online Nordic grocers. They’re the key to getting that gently sweet, savoury, unmistakably Nordic flavour.