076 / 100 · Sides Worth Passing Around

Scalloped Potatoes with Leeks

6 side-dish portions Active 25 min Total 1 hr 45 min

Thin potato slices and sweet leeks settle into a creamy bake with a lightly golden Parmesan top. The sauce is thickened on the stovetop before it meets the potatoes, which helps it coat each layer instead of collecting at the bottom of the dish. Leeks bring a mild onion flavor, but their layers hide grit, so give them a proper rinse after slicing. This is a comfortable side for a long dinner, especially when something else in the meal can be prepared while the potatoes bake.

Jump to the ingredients

Creamy scalloped potatoes and leeks with a golden Parmesan crust.

Consistent slices make a dependable bake

A mandoline makes quick work of the potatoes, but a sharp knife is perfectly workable. Aim for slices about an eighth of an inch thick and keep that thickness consistent. Very thick slices remain firm after the sauce bubbles; extremely thin ones can collapse into a mash. Do not rinse the sliced potatoes, because their surface starch helps the sauce cling. Slice them near assembly time so they do not sit exposed and discolor.

Covered first, golden last

The foil traps steam for the first part of baking, helping the middle layers become tender. Uncover only after a knife can pass most of the way through with little resistance. The final uncovered stage colors the Parmesan and reduces the sauce slightly. Give the dish a short rest before spooning: the starches settle and the sauce becomes less fluid. If you need especially neat squares, let it rest longer, though a gently flowing spoonful is part of its appeal.

Ingredients

  • 2 tablespoons unsalted butter (28 g), plus a little for the dish
  • 2 medium leeks, white and light green parts only, thinly sliced and thoroughly washed (250 g)
  • 2 tablespoons all-purpose flour (16 g)
  • 2 cups whole milk (480 ml)
  • 1/2 cup heavy cream (120 ml)
  • 3/4 teaspoon fine salt
  • 1/8 teaspoon freshly grated nutmeg
  • 2 pounds Yukon Gold potatoes, peeled and sliced 1/8 inch thick (900 g)
  • 1/2 cup finely grated Parmesan (40 g)

Set out

2-quart baking dish, approximately 8 by 11 inches, Medium saucepan, Large skillet, Whisk, Foil, Mandoline with guard or sharp knife

Allergens

Milk, wheat. Check ingredient labels and substitutions.

Make it

  1. Heat the oven to 375°F/190°C. Butter a 2-quart baking dish. Drain the washed sliced leeks well.
  2. Melt the 2 tablespoons butter in a large skillet over medium-low heat. Add the leeks and cook for 8–10 minutes, stirring, until soft but not brown.
  3. Sprinkle the flour over the leeks and stir for 1 minute. Gradually whisk in the milk, then the cream. Add the salt and nutmeg. Simmer gently for 2–3 minutes, stirring, until lightly thickened.
  4. Spread one-third of the potatoes in the dish. Spoon over one-third of the leek sauce. Repeat twice, gently spreading the last sauce layer over all exposed potato edges.
  5. Cover tightly with foil and bake for 45–50 minutes. Carefully lift the foil and test the middle with a thin knife; continue covered if the potatoes are still firm.
  6. Scatter with Parmesan and bake uncovered for 15–20 minutes more, until golden and the potatoes are completely tender.
  7. Rest for 10 minutes before serving.

A useful detail

A dish much smaller or deeper than 2 quarts can leave the central layers undercooked; use the listed size and check the center with a knife.

Make it your own

  • Use 1/2 cup (50 g) finely shredded Gruyere instead of Parmesan.
  • Add 1 teaspoon fresh thyme leaves to the leek sauce after thickening.

Keep it well

Refrigerate in shallow portions within 2 hours, or 1 hour above 90°F/32°C, at 40°F/4°C or colder for up to 4 days. Reheat covered portions to 165°F/74°C. Freezing can make the sauce slightly grainy.