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Old-Fashioned Scalloped Potatoes

G By Our Grannies' Kitchen Updated Jul 2026 4.8 (287 ratings)
Old-Fashioned Scalloped Potatoes
Old-Fashioned Scalloped Potatoes
4.8 / 5
8 servings

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Ingredients

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  • 3 ¼ lb (1.5 kg) floury potatoes (Maris Piper or King Edward), sliced 3–4 mm
  • 1 medium onion (about 150 g), finely chopped
  • ½ stick (60 g) butter and 45 g all-purpose flour
  • 3 ⅛ cups (750 ml) whole milk, warmed
  • 1½ tsp fine salt, ½ tsp pepper and a small grating of nutmeg
  • ½ cup (50 g) mature cheddar, grated (optional, for the top)

Method

  1. Slice. Oven to 350°F (180°C, fan 160°C); butter a 2.5 liter baking dish. Slice the peeled potatoes 3–4 mm thick — mandoline or your steadiest knife — and don't rinse them: the starch clinging to the slices is what thickens the sauce.
  2. Make the sauce. Melt the butter, soften the onion for 5 minutes without coloring, then stir in the flour for 1–2 minutes. Whisk in the warm milk a little at a time and simmer gently 2–3 minutes — it should coat a spoon but still pour easily. Season with the salt, pepper & nutmeg.
  3. Layer. A third of the potatoes in the dish, overlapping like roof tiles, then a third of the sauce; repeat twice more, finishing with sauce and nudging every slice under it.
  4. Bake covered. Foil on tight; 45 minutes, until a small knife slips through the middle with no resistance.
  5. Uncover and brown. Foil off, scatter over the cheddar if using, and bake 35–40 minutes more, until deep golden and bubbling at the edges.
  6. Rest. 10–15 minutes on the side, uncovered. The sauce thickens from pourable to spoonable — don't skip it.
Granny's tip

Granny set the milk in a pan at the back of the stove while she sliced — warm milk whisked into the roux makes a smooth sauce in two minutes flat, with no lumps to chase round the pan.

Tips for perfect scalloped potatoes

Slice thin and even

3–4 mm, every slice the same. A mandoline makes it foolproof — uneven slices are why some patches stay crunchy while others collapse.

Foil first, brown later

Covered, the potatoes steam gently until tender; uncovered, the top turns deep golden. Skip the foil and the top dries out before the middle cooks.

Rest before serving

Straight from the oven the sauce is thin. Give it 10–15 minutes and it thickens to a proper creamy coat that holds its layers on the spoon.

Questions, answered

Why are my scalloped potatoes still crunchy?

Almost always the slices were too thick or uneven — anything over about 4 mm needs far longer than the recipe allows, and mixed thick-and-thin slices cook at different rates. The other culprit is an oven that is too hot, which browns the top and dries the sauce before the middle is cooked. Slice 3–4 mm, bake at 350°F (180°C) covered with foil for the first 45 minutes, and test with a knife before you uncover.

Why did my sauce curdle or split?

Usually the milk boiled hard, either on the stovetop or in too hot an oven — dairy that boils hard separates into grainy curds and watery liquid. Low-fat milk splits far more readily than whole milk, so use whole milk, bring the sauce only to a gentle simmer, and keep the oven at 350°F (180°C) or below. The flour in the sauce is your insurance: whisked in properly, it stabilises the milk through the long bake.

What is the difference between scalloped potatoes and potatoes au gratin?

The sauce. True old-fashioned scalloped potatoes are layered with a plain white sauce of butter, flour and milk — no cheese. Au gratin potatoes have cheese melted through the layers and a browned cheese or breadcrumb top. A small handful of cheddar scattered over scalloped potatoes for the last stretch of baking is a common family liberty, but the dish itself is the creamy one, not the cheesy one.

Can I make scalloped potatoes ahead and reheat them?

Yes — bake the dish fully, cool, cover and refrigerate for up to 2 days. Reheat covered with foil at 325°F (160°C) (fan 275°F (140°C)) for 30–35 minutes until piping hot in the center, adding a splash of milk around the edges if it looks dry. Don't assemble it raw ahead of time: cut potatoes discolor and weep water into the sauce. Freezing isn't recommended — the milk sauce tends to split and the potatoes turn grainy on thawing.

From Granny's Pantry

The know-how behind this recipe:

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