Cheesy Scalloped Potatoes

Name: Cheesy Scalloped Potatoes
Prep time: 30 min
Cook time: 1 h 25 min
Total time: 1 h 55 min
Yield: 8 servings
Cuisine: American
Ingredients: 3 tbsp (43 g) unsalted butter, plus 1 teaspoon (5 g) extra, softened, for greasing the dish; 1 medium (about 8 oz / 225 g) (225 g) yellow onion, finely chopped; 3 cloves (10 g) garlic cloves, minced; 3 tbsp (24 g) all-purpose flour; 2 cups (480 ml) heavy cream, at room temperature or cool, not ice-cold; 1 cup (240 ml) whole milk; 2 tsp (8 g) kosher salt, Diamond Crystal; use 1 1/4 tsp if using fine table salt; ½ tsp (1 g) black pepper, freshly ground; ¼ tsp (½ g) ground nutmeg; 2 tsp (3 g) fresh thyme leaves, stripped from the stems (optional); 3 cups (300 g) sharp cheddar cheese, freshly grated from a block (about 10 oz / 300 g), divided: 2 cups (200 g) for the sauce, 1 cup (100 g) for the top; 3 lb (1360 g) russet potatoes, peeled, sliced 1/8 inch (3 mm) thick; do not rinse or soak

From the MyKitchenBank Kitchen

Thinly sliced russet potatoes baked in a silky onion-cheddar cream sauce until tender, bubbling, and golden on top. A make-ahead-friendly side for holidays and Sunday dinners.

Prep: 30 min
Cook: 1 hr 25 min
Wait: 15 min
Total: 2 hr 10 min
Makes: 1 casserole (8 generous servings)

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Ingredients

8 servings

3 tbsp (43 g) unsalted butter, plus 1 teaspoon (5 g) extra, softened, for greasing the dish
1 medium (about 8 oz / 225 g) (225 g) yellow onion, finely chopped
3 cloves (10 g) garlic cloves, minced
3 tbsp (24 g) all-purpose flour
2 cups (480 ml) heavy cream, at room temperature or cool, not ice-cold
1 cup (240 ml) whole milk
2 tsp (8 g) kosher salt, Diamond Crystal; use 1 1/4 tsp if using fine table salt
½ tsp (1 g) black pepper, freshly ground
¼ tsp (0.5 g) ground nutmeg
2 tsp (3 g) fresh thyme leaves, stripped from the stems (optional)
3 cups (300 g) sharp cheddar cheese, freshly grated from a block (about 10 oz / 300 g), divided: 2 cups (200 g) for the sauce, 1 cup (100 g) for the top
3 lb (1360 g) russet potatoes, peeled, sliced 1/8 inch (3 mm) thick; do not rinse or soak

Equipment (7)

9×13-inch (23×33 cm) baking dish, 3 quarts
Large heavy saucepan (3-4 quart)
Mandoline or sharp chef's knife
Whisk
Box grater
Aluminum foil
Rimmed baking sheet (to catch drips)

Steps

Before you start

Grate the cheddar from a block yourself; pre-shredded cheese contains starch that can make the sauce grainy.
Position an oven rack in the center and preheat to 375°F (190°C).
A mandoline makes evenly thin slices quickly. Use the guard, and if slicing by hand, use a sharp knife and aim for 1/8 inch (3 mm).
Plan on about 2 hours total, including a 15-minute rest before serving.

1
Prep oven and dishOven 375°F / 190°C
- Position a rack in the center of the oven and heat to 375°F (190°C).
- Grease the bottom and sides of a 9×13-inch (23×33 cm) baking dish with the 1 teaspoon softened butter.
- Set the dish on a rimmed baking sheet.
- Grate the cheddar and divide it into 2 cups for the sauce and 1 cup for the top.
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Ready when: Dish is evenly coated with a thin film of butter.
Tip: The baking sheet catches any bubbling sauce and saves you from scrubbing the oven.
2
Slice the potatoes
- Peel the potatoes and slice them crosswise 1/8 inch (3 mm) thick with a mandoline or sharp knife.
- Place the slices in a large bowl as you go.
- Do not rinse or soak them; the surface starch helps thicken the sauce.
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Ready when: Slices are uniform and flexible, and you can almost see light through them.
Tip: Uneven slices cook unevenly, so discard the thick end pieces or re-slice them thinner.
3
Cook onion and garlic
- Melt the 3 tablespoons butter in a large heavy saucepan over medium heat.
- Add the chopped onion and 1/4 teaspoon of the salt.
- Cook, stirring often, for 6 to 8 minutes.
- Add the garlic and cook for 30 seconds, until fragrant.
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Ready when: Onion is soft and translucent with no browning; garlic smells fragrant.
Tip: Do not let the garlic brown, or it will taste bitter.
4
Make the roux
- Sprinkle the flour over the onions and stir constantly for 1 minute to cook out the raw flour taste.
- The mixture will look like a thick, pale paste.
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Ready when: Mixture is pasty and smells lightly toasty, not raw.
5
Build the cream sauce
- Slowly pour in the milk while whisking constantly, then whisk in the cream.
- Add the remaining salt, the pepper, nutmeg, and thyme if using.
- Raise the heat to medium-high and bring to a gentle simmer, whisking often.
- Reduce the heat to medium-low and simmer for 3 to 4 minutes.
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Ready when: Sauce lightly coats the back of a spoon and holds a clear line when you draw a finger through it.
Tip: Add the milk gradually to prevent lumps, and do not let the sauce boil hard.
6
Melt in the cheese
- Remove the pan from the heat.
- Stir in 2 cups (200 g) of the cheddar a handful at a time until smooth.
- Taste and adjust the salt; the sauce should taste slightly salty because the potatoes will absorb seasoning.
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Ready when: Sauce is smooth, glossy, and fully melted with no visible strands of cheese.
Tip: Adding cheese off the heat prevents the sauce from separating or turning greasy.
7
Coat the potatoes
- Pour the warm sauce over the potato slices in the large bowl.
- Gently toss with your hands or a spatula for about 1 minute so every slice is coated and the slices separate.
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Ready when: No dry slices remain, and the sauce is evenly distributed.
8
Assemble the casserole
- Transfer the potatoes and sauce to the prepared dish.
- Spread into an even layer and press down firmly so the potatoes are mostly submerged.
- Scrape any sauce left in the bowl on top.
- Cover tightly with foil.
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Ready when: Surface is level and sauce reaches nearly to the top layer of potatoes.
Tip: Tent the foil slightly so it does not stick to the potatoes.
9
Bake coveredOven 375°F / 190°C
- Bake the covered casserole at 375°F (190°C) for 45 minutes.
- This steams the potatoes so they cook through without drying out.
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Ready when: Sauce is bubbling around the edges and a knife slides into the potatoes with slight resistance.
10
Top and brownOven 375°F / 190°C
- Carefully remove the foil, watching for steam.
- Sprinkle the remaining 1 cup (100 g) cheddar evenly over the top.
- Bake uncovered at 375°F (190°C) for 30 to 35 minutes more.
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Ready when: Top is golden brown with bubbling edges, and a paring knife slides into the center with no resistance.
Tip: If the top browns too fast before the potatoes are tender, loosely re-cover with foil.
11
Rest before serving
- Let the casserole rest on a wire rack for 15 minutes.
- The sauce will thicken and set so the portions hold together when scooped.
- Serve warm.
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Ready when: Sauce no longer runs when you cut into the casserole.
Tip: Skipping the rest gives you soupy scalloped potatoes.

Good to know

Tips

Slice thickness matters most: 1/8 inch (3 mm) slices cook through in the time given, and thicker slices may stay firm.
Don't rinse the sliced potatoes. Their starch is what thickens the sauce.
Keep the sauce at a gentle simmer and add cheese off the heat to avoid a broken, greasy sauce.
Test doneness in the center of the dish, not the edges, since edges cook faster.

Make ahead

"Assemble the casserole through step 8, cool the sauce slightly first, cover tightly, and refrigerate up to 24 hours. Add 10 to 15 minutes to the covered baking time since it starts cold. Alternatively, bake fully, cool, and refrigerate up to 2 days, then reheat as described under storage."

Storage & reheating

"Room temperature: up to 2 hours after baking. Refrigerator: cover and store up to 4 days. Freezer: freeze portions in airtight containers up to 2 months (texture is slightly softer); thaw overnight in the fridge. Reheat covered with foil at 350°F (175°C) for 20 to 30 minutes, or until hot in the center, uncovering for the last 5 minutes. Single portions can be microwaved at 70% power in 1-minute bursts."

Substitutions

russet potatoes → Yukon Gold potatoes. Use the same weight. They hold their shape better and have a buttery flavor, but give a slightly less thick sauce.
sharp cheddar cheese → Gruyère or a mix of Gruyère and cheddar. Use the same weight for a nuttier, more complex flavor that melts smoothly.
heavy cream → Additional whole milk (total 3 cups / 720 ml plus 1 extra tbsp flour). Gives a lighter result that is less rich, and the sauce is slightly more likely to curdle, so keep the heat gentle.
fresh thyme leaves → 1/2 tsp dried thyme or 1 tsp chopped fresh chives. Dried thyme is stronger, so use less.