Cheesy Scalloped Potatoes

Ingredients

• 4russet potatoes, peeled and sliced into 6 mm slices
• 1yellow onion, sliced into rings
• 43 g (3 tablespoons)unsalted butter
• 24 g (3 tablespoons)plain flour
• 2.5 ml (½ teaspoon)kosher salt
• 480 ml (2 cups)whole milk, at room temperature
• 170 g (1½ cups)mild Cheddar cheese, grated

Instructions

1. 1

   Heat the oven

   Preheat the oven to 204°C (400°F). Lightly coat a 20 × 20 cm (8 × 8-inch) casserole dish with non-stick cooking spray.

2. 2

   Layer the vegetables

   Arrange the sliced potatoes and onion rings in the prepared dish, alternating and overlapping them so they are spread evenly.

3. 3

   Make the roux

   Melt the butter in a saucepan over medium heat. Whisk in the flour and salt continuously for 1 minute.

4. 4

   Finish the sauce

   Add the milk gradually and cook until the mixture thickens. Take the pan off the heat and stir in the cheese until melted.

5. 5

   Add the sauce

   Pour the cheese sauce over the potatoes and onions, then cover the dish with foil.

6. 6

   Bake until tender

   Bake for 85–90 minutes, until a fork pierces the potatoes easily.

7. 7

   Brown the top

   If you like, place the dish under the grill for a few minutes to crisp the top.

8. 8

   Season and serve

   Season with salt and pepper to taste before serving.

What are scalloped potatoes?

Scalloped potatoes are a familiar American baked side dish made from thinly sliced potatoes cooked in a creamy sauce. This version adds onion and mild Cheddar for a savoury, cheesy finish.

The method builds flavour with a simple butter-and-flour sauce rather than relying on cream. Layering the slices evenly helps them cook at a similar pace.

Nutrition and macros by portion

The nutrition label shows one serving as written: 310 calories, 10g protein, 34g carbs, 15g fat.

The potatoes provide most of the carbohydrates, while butter, milk and Cheddar contribute much of the fat; the cheese and milk also supply protein. Serve a portion with green vegetables and a lean protein for a more balanced plate.

Choosing and preparing the potatoes

Russet potatoes: their starchy texture suits a long bake and helps the sauce cling to the slices. Peel them and cut them into even 6 mm slices so they soften uniformly.

Onion: rings tucked between the potatoes add savoury flavour throughout the dish. Distribute them across the layers rather than leaving them in one thick patch.

Getting a smooth cheese sauce

Roux: whisk the flour into the melted butter and cook it for the full minute, keeping it moving so it does not catch. This step helps the sauce thicken without tasting floury.

Milk and cheese: add the room-temperature milk gradually while stirring, then remove the pan from the heat before adding the grated Cheddar. Stir until the cheese melts into the thickened sauce.

Baking for tender layers

Covered baking: foil keeps the dish covered as the potatoes cook through during the long bake. Bake for 85–90 minutes at 204°C (400°F), checking tenderness with a fork.

Crisp finish: the optional grill step adds colour to the top. Watch closely while grilling, as the surface can brown quickly.

Timing and making ahead

Allow the full baking time, since the potato slices need time to soften beneath the foil. A fork should slide through a slice easily before you take the dish out.

For a head start, arrange the potatoes and onions in the dish and prepare the sauce ahead, then assemble and bake when ready. Keep prepared ingredients covered and chilled until baking.

What to serve alongside

Pair the rich, cheesy potatoes with a green vegetable such as green beans or broccoli, or serve them alongside a crisp salad. Their creamy texture also works well with roast chicken or another simply cooked main.

Recipe notes & tips

• Slice the potatoes evenly so they become tender at roughly the same time.
• Use room-temperature milk and add it gradually to help the sauce come together smoothly.
• Keep whisking the butter, flour and salt for the full minute.
• Spread the onion rings between the potato slices for flavour throughout the dish.
• Check tenderness with a fork before taking the casserole out of the oven.
• Stay by the oven during the optional grill step and remove the dish once the top is crisp.

Variations

• Use sharper Cheddar: swap the mild Cheddar for a stronger variety for a more pronounced cheese flavour.
• Add garlic: stir a little finely chopped garlic into the butter before adding the flour.
• Include fresh herbs: scatter chopped thyme or parsley between the potato layers.
• Add a crunchy top: finish with a handful of breadcrumbs before the optional grill step.
• Mix the cheeses: replace some of the Cheddar with another good-melting cheese.

Common mistakes to avoid

• Uneven slices: thick pieces take longer to cook, so aim for consistent 6 mm slices.
• Lumpy sauce: add the milk gradually and whisk as you pour.
• Scorched roux: keep whisking the butter, flour and salt over medium heat for the full minute.
• Cheese sauce split: take the pan off the heat before stirring in the cheese.
• Undercooked potatoes: test the centre with a fork and continue baking until the slices are tender.
• Burnt topping: watch the dish closely under the grill, where browning happens quickly.

How to store

Cool leftovers and store them covered in the fridge for up to 3 days. Reheat in a covered ovenproof dish until hot throughout, or microwave individual portions; add a splash of milk if the sauce seems too thick.

Frequently asked questions