Swedish Jansson’s Temptation Potato Gratin

Why You’ll Love This Recipe

• Classic Swedish comfort: silky potatoes, sweet onions, and savory spiced sprats in a creamy blanket.
• A golden, buttery breadcrumb crust that stays crisp over a luscious interior.
• Balanced salty-sweet flavors thanks to the ansjovis marinade and gentle white pepper.
• Perfect make-ahead gratin that pairs beautifully with a crisp green salad.

Grocery List

• Produce: 2 lb starchy potatoes, 2 medium yellow onions, fresh dill or parsley (optional)
• Dairy: Heavy cream, whole milk, unsalted butter
• Pantry: Swedish spiced sprats (ansjovis), fine dry breadcrumbs, white pepper, kosher salt

Full Ingredients

For the gratin

• 2 lb (900 g) starchy potatoes (Russet, Maris Piper, or King Edward), peeled and cut into 1/4-inch (6 mm) matchsticks
• 2 medium yellow onions (about 1 lb/450–500 g), thinly sliced
• 3 tbsp unsalted butter, divided, plus extra for greasing the dish
• 1 tin (4.4 oz/125 g) Swedish spiced sprats (ansjovis), drained; reserve 3 tbsp marinade; cut fillets into thirds
• 1/4 tsp white pepper
• Pinch kosher salt, to taste (the sprats are salty; add only if needed)

For the cream mixture

• 1 1/2 cups (360 ml) heavy cream
• 1/4 cup (60 ml) whole milk
• 3 tbsp reserved ansjovis marinade
• 1/4 tsp white pepper
• Optional: tiny pinch sugar (1/4 tsp) if your sprats are particularly briny

For the topping

• 1/2 cup (30 g) fine dry breadcrumbs
• 1 tbsp unsalted butter, melted (to toss with breadcrumbs)
• 1 tbsp unsalted butter, cut into small pieces (to dot on top)

To serve (optional)

• Chopped fresh dill or flat-leaf parsley
• Crisp green salad with lemony vinaigrette

Step-by-Step Instructions

Step 1: Heat the oven and prepare the dish

Set a rack in the center of the oven and preheat to 400°F (200°C). Generously butter a 2-quart (2 L) gratin or casserole dish. This helps prevent sticking and encourages the classic browned crust around the edges.

Step 2: Prep the potatoes

Peel the potatoes and cut into even matchsticks about 1/4-inch (6 mm) thick. If your potatoes are very starchy, you may briefly rinse or soak them for 5 minutes in cold water to remove excess surface starch. Drain and thoroughly pat dry with clean towels; too much water will thin the cream.

Step 3: Soften the onions

In a skillet over medium heat, melt 1 tablespoon of the butter. Add the sliced onions and a pinch of salt. Cook, stirring occasionally, until soft and pale golden, 8–10 minutes. Stir in 1/8 teaspoon white pepper, then remove from heat.

Step 4: Layer the gratin

Spread half the potatoes in the prepared dish. Top with half the onions and half the sprats. Repeat with remaining potatoes, onions, and sprats, finishing with a final layer of potatoes. Season the top lightly with the remaining white pepper (and only a tiny pinch of salt if needed).

Step 5: Mix the cream and pour

Whisk the heavy cream, milk, and 3 tablespoons reserved ansjovis marinade. Taste: it should be pleasantly savory with a subtle sweet-spiced note; add a tiny pinch of sugar if too briny. Pour evenly over the potatoes. Press the top gently with a spatula to settle the layers. The liquid should come about three-quarters of the way up the top layer—add a splash of cream if very low.

Step 6: Bake covered, then add the crumb topping

Cover the dish tightly with foil and bake 35 minutes. Meanwhile, toss breadcrumbs with 1 tablespoon melted butter. Remove foil, scatter the buttered crumbs evenly over the top, and dot with the remaining 1 tablespoon butter. Return to the oven and bake uncovered 25–35 minutes, until the top is deep golden and the edges are bubbling. A knife should slide easily through the potatoes in the center. If the top browns too quickly, tent loosely with foil for the final 10 minutes.

Step 7: Rest and serve

Let the gratin rest 10 minutes to set. Sprinkle with chopped dill or parsley. Serve warm with a crisp green salad to balance the richness.

Pro Tips

• Use Swedish spiced sprats labeled ansjovis; Mediterranean anchovies are much saltier and lack the gentle sweet-spiced brine.
• Even potato size is key for tenderness; a mandoline with a julienne blade makes quick, uniform matchsticks.
• Taste your cream-and-marinade mixture before pouring; it should be savory, not aggressively salty.
• If the gratin looks dry after the first bake, add 2–4 tbsp extra cream around the edges before adding the crumbs.
• Resting time helps the layers settle for clean slices and a silky texture.

Variations

• Without fish (falsk Jansson): Replace sprats with 2 tbsp capers and 1 tsp finely chopped nori; add a pinch of allspice and 1/2 tsp sugar to the cream.
• Leek and potato: Swap one onion for 1 large leek (white and light green parts), sautéed gently in butter.
• Individual portions: Build and bake in 6 small buttered ramekins; reduce uncovered bake time by about 10 minutes.

Storage & Make-Ahead

Refrigerate leftovers in an airtight container up to 3 days. Reheat, covered, at 350°F (180°C) for 20–25 minutes, then uncover for 5 minutes to re-crisp the crumbs. Make-ahead: Assemble through Step 5 up to 6 hours ahead; cover and refrigerate. Bake straight from the fridge, adding 5–10 minutes to the covered bake time. Freezing isn’t ideal for potatoes, but if needed, par-bake covered for 25 minutes, cool completely, wrap well, freeze up to 1 month, thaw overnight, then add crumbs and finish baking.

Nutrition (per serving)

Approximate: 480 calories; 31 g fat; 38 g carbohydrates; 9 g protein; 980 mg sodium; 3 g fiber. Values will vary with specific brands and how much marinade you include.