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Scalloped Potatoes Recipe

Make this Scalloped Potatoes Recipe for creamy, layered potatoes baked to golden perfection.

Ingredients

• 1 tablespoon (14 g) unsalted butter, softened, for greasing the baking dish
• 3 pounds (1.4 kg) Yukon Gold or Russet potatoes, peeled and sliced 1/8 inch (3 mm) thick
• 4 tablespoons (56 g) unsalted butter, cut into pieces, for the sauce
• 1 medium yellow onion (about 6 oz / 170 g), very thinly sliced
• 2 cloves garlic (about 8 g), finely minced
• 4 tablespoons (30 g) all-purpose flour
• 2 cups (480 ml) whole milk, at room temperature
• 1 1/2 cups (360 ml) heavy cream, at room temperature
• 2 teaspoons (2 g) fresh thyme leaves, finely chopped, or 1/2 teaspoon (0.5 g) dried thyme
• 2 1/4 teaspoons (13 g) kosher salt, divided, plus more to taste
• 1 teaspoon (2 g) freshly ground black pepper, divided
• 1/8 teaspoon (0.3 g) ground nutmeg (optional, but recommended)
• 1 1/2 cups (150 g) grated Gruyère or sharp white cheddar cheese, divided (optional, for a cheesy variation)
• 2 tablespoons (4 g) finely chopped fresh chives or flat-leaf parsley, for garnish (optional)

Instructions

Step 1: Preheat and grease the baking dish

Preheat the oven to 350°F (175°C) and lightly coat a 9x13-inch rectangular baking dish with 1 tablespoon softened unsalted butter, making sure the bottom and sides are evenly greased so nothing will stick. This small, careful step sets the stage for even browning and clean slices later; a lightly buttered rim helps the sauce cling to the potato edges.

Step 2: Peel and slice the potatoes thinly

Peel 3 pounds of Yukon Gold or Russet potatoes and slice them into very even 1/8-inch (3 mm) rounds using a sharp knife or mandoline. Keep the slices uniform for consistent cooking—stack them neatly on a plate as you work, and if you pause, submerge the slices briefly in cold water to prevent browning. When ready to assemble, drain and pat the rounds completely dry so they won’t water down the sauce.

Step 3: Soften the onions in butter

Melt 4 tablespoons of butter in a pan until it shimmers, then add one very thinly sliced yellow onion and cook gently until translucent and soft, about 5–7 minutes; you want glossy, tender ribbons of onion without any brown bits, bright and buttery in appearance. Stir in minced garlic for just a brief fragrant moment, being careful the garlic never darkens—this step leaves you with soft, sweet onions suspended in butter.

Step 4: Build the roux and incorporate the cream mixture

Sprinkle in 4 tablespoons of flour and cook with the onions for 1–2 minutes until the mixture looks slightly foamy and nutty. Slowly whisk in the combined whole milk and heavy cream in several additions until perfectly smooth, then add salt, a little black pepper, chopped fresh thyme and a whisper of nutmeg. Simmer gently, whisking often, until the sauce thickens to coat the back of a spoon; if using the cheesy variation, stir in 1/2 cup grated cheese now so it melts silky and smooth. The finished sauce should be glossy, slightly viscous, and pale ivory.

Step 5: Taste and adjust the sauce

Carefully taste the warm cream sauce and tweak seasoning—add a pinch more salt or pepper if needed. The texture should be velvety and clingy, thick enough to sit between slices without pooling into a watery puddle. Keep the sauce warm and ready for assembly; its sheen and thickness are the key visual and mouthfeel anchors for the finished dish.

Step 6: Dry the potato slices and start the first layer

Drain any soaking water from the potato slices and pat them completely dry with clean towels so the sauce can adhere. Arrange one-third of the potato rounds in an even, slightly overlapping layer across the bottom of the buttered rectangular dish; finish this layer with a light pinch of the reserved salt and pepper, and spoon about one-third of the hot cream sauce over so it seeps between the slices. If using cheese, scatter roughly one-third of the grated cheese over this first layer to begin forming those golden pockets of melted cheese.

Step 7: Repeat layering and complete the top

Add the second overlapping layer of potatoes, season lightly again, pour another third of the sauce evenly, and sprinkle the next third of cheese if desired. Finish with the final layer of potato rounds, season, pour the remaining sauce so every slice is coated, and distribute the remaining cheese evenly across the surface. The assembled, uncooked casserole should look compact, creamy and slightly glossy with visible ridges of overlapping potato; cover the dish loosely with foil, tenting so it won’t press on the surface.

Step 8: Bake until tender and finish the top

Bake covered at 350°F for about 45 minutes so the potatoes steam and soften, then remove the foil and continue baking uncovered for 30–40 minutes until the top turns deep golden brown and the sauce bubbles at the edges. If extra browning is desired, a quick 2–3 minute broil will crisp the peaks—watch closely so the top goes golden, not burnt. The visual milestone here is the transformation from pale assembled layers to a bubbling, bronzed surface that promises creamy tender slices beneath.

Step 9: Rest, garnish, cut and serve

Remove the dish from the oven and let it rest 15–20 minutes so the sauce sets for cleaner slices. Just before serving, sprinkle 2 tablespoons finely chopped chives or parsley for a bright green contrast. For neat portions, cut into squares and lift each piece from the rectangular dish with a spatula, making sure to scoop from the bottom so every portion carries the creamy sauce.

Notes

• Use a mandoline for ultra-even potato slices but protect your fingers.
• Pat potato slices completely dry to prevent a watery sauce.
• Let the casserole rest 15–20 minutes after baking for cleaner slices.
• To make ahead, assemble and refrigerate for up to 24 hours before baking.
• For a cheesy version, fold in grated cheese into the sauce and between layers.