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Sides · American

Scalloped Potatoes

Thin potato slices baked slowly in an onion-scented white sauce until tender and bubbling.

Hands-on
30 min
Hands-off
1 h 35 min
Oven preheat
15 min
Total
2 h 5 min
Makes
6 servings
Serves
6

2 h 5 min: 20 min slicing, about 10 min making the sauce on the stove (the oven heats meanwhile), 30 min covered + 60 min uncovered bake, 5 min rest. If the potatoes need the full extra 10 min and a 10 min rest, allow 2 h 20 min.

Oven 180 °C · 160 °C fan (350 °F)

Pan 2 L (2-quart) casserole dish (US: 2-quart casserole dish)

  • easy
  • vegetarian
  • thanksgiving
  • holiday
  • side-dish

Verified against at least two trusted test kitchens or food-safety guides · Last checked · What this means

Illustration of Scalloped Potatoes
Amount
Units
Oven

Ingredients

You need: 2-quart (about 2 L) casserole dish · 2-quart (about 2 L) saucepan · whisk · silicone spatula · vegetable peeler · sharp knife or mandoline with hand guard · aluminium foil · fork for testing · oven mitts

Contains: milk · wheat

Method

  1. Heat the oven, grease the dish

    Heat the oven to 180°C (160°C fan, 350°F). Grease a 2-quart (about 2 L) casserole dish well with shortening or cooking spray.

  2. Soften the onion

    Melt 3 tbsp (43 g) of the butter in a 2-quart saucepan over medium heat. Add the chopped onion and cook for about 2 minutes, stirring now and then.

    Ready when: The onion is soft and tender but not browned.

  3. Cook the flour

    Whisk in 23 g (3 tbsp) flour, 1 tsp salt and 1/4 tsp pepper. Keep stirring until the mixture is smooth and bubbly, then take the pan off the heat.

    Ready when: A smooth paste with small bubbles all over and no dry flour left.

  4. Make the sauce

    Whisk in the 590 ml (2 1/2 cups) milk. Put the pan back over medium heat and bring it to a boil, stirring all the time. Boil and stir for 1 minute. Take it off the heat and cover it while you slice the potatoes.

    Ready when: It bubbles across the whole surface and has thickened slightly, about like going from skim milk to cream.

  5. Slice the potatoes

    Wash the 907 g (2 lb) potatoes, peel them if you like, rinse, and slice them evenly about 3 mm (1/8 in) thick.

    Otto tried this firstOtto hacks the potatoes into slices of every thickness. The thick ones are still hard when the thin ones are done, so the slices need to be an even 1/8 inch.

  6. Assemble

    Spread the slices in the greased dish. Pour the hot sauce evenly over them so they are covered. Cut the last 1 tbsp (14 g) butter into small pieces and scatter them on top.

  7. Bake covered

    Cover the dish with foil and bake for 30 minutes.

    Ready when: Not done yet: the sauce is just starting to bubble at the edges and the potatoes are still firm.

  8. Bake uncovered

    Remove the foil (carefully: hot steam) and bake for 1 hour to 1 hour 10 minutes more.

    Ready when: A fork pushed all the way down slides into the bottom slices as easily as the top ones. The sauce bubbles at the edges and the top is golden in places.

  9. Rest

    Let the dish stand for 5 to 10 minutes before serving. The sauce thickens as it rests.

Swaps

  • Instead of 2% milk: whole milk, same amount Whole milk gives a richer sauce.
  • Instead of plain top: a sprinkling of Parmesan or grated Gruyère, or breadcrumbs, before baking

Make ahead, store & reheat

Make ahead
Assembling ahead isn't recommended: the potatoes soak up the sauce and turn dry. Instead, slice the potatoes and keep them covered in cold water in the fridge for up to 24 hours, then drain them very well and assemble just before baking.
Storage
Cover and refrigerate within 2 hours of serving. Eat within 3 to 4 days (some recipes allow up to a week; we use the stricter food-safety guidance). Freezing isn't recommended: the potatoes turn mealy and the sauce over-thickens.
Reheat
Several portions: put them in a greased oven dish, cover tightly with foil and bake at 180°C (160°C fan, 350°F) for 20 to 30 minutes. One portion: microwave loosely covered at 70% power for about 2 minutes. Either way, heat until hot all the way through, 74°C (165°F).

If something goes wrong

  • Sauce baked onto the sides of the dish Why: Dish not greased well.
    Grease the whole inside of the dish generously.
  • Bottom potatoes still hard Why: Thick or uneven slices.
    Slice evenly about 3 mm (1/8 in); a mandoline helps. Keep baking and test the bottom layer with a fork.
  • Dry potatoes Why: Slices not covered by sauce, or assembled too early.
    Pour the hot sauce straight over the slices so they're covered, and bake right after assembling.

Good to know

  • Make the sauce in a 2-quart saucepan: a much smaller or larger pan changes how thick it gets.
  • Taste for salt: under-salted scalloped potatoes taste flat.

Safety

  • Mandoline blades are extremely sharp. Always use the hand guard, and kids shouldn't use one.
  • The dish, the foil steam and the bubbling sauce are very hot. Lift the foil away from you and use oven mitts; kids should let an adult handle the dish.
  • This dish contains milk: refrigerate leftovers within 2 hours.