Do I have to use a mandoline for these scalloped potatoes?

No, but the slices must be evenly 1/8 inch thick, whichever tool you use. A mandoline simply makes evenness automatic. With a knife, halve each potato so it sits flat, slice slowly, and check your thickness against a ruler for the first few slices until your hands learn it.

Can I assemble healthy scalloped potatoes the day before Thanksgiving?

Yes, and the flavor improves for it. Assemble the dish completely in its sauce, cover tightly and refrigerate for up to 24 hours. Let it stand at room temperature for 30 minutes before baking, and add about 10 minutes to the covered bake since it starts cold.

Why did the sauce in my scalloped potatoes turn out watery?

The usual cause is slices that went into the dish still wet from soaking, which dilutes the sauce as it bakes. Pat the slices dry, and rest the finished gratin for a full 15 minutes, because the potatoes keep absorbing sauce as they stand and the texture firms up noticeably.

Can I freeze scalloped potatoes?

It is not recommended. Milk based sauces separate on thawing and the potato slices turn grainy, so the dish loses the texture that makes it worth serving. Leftovers keep well for 3 days in the fridge and reheat covered at 350 degrees Fahrenheit for about 20 minutes.

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

Traditionally, scalloped potatoes are baked in a milk or cream sauce with no cheese, while au gratin adds cheese and often a browned crumb top. This recipe sits between the two: a milk sauce like a classic scalloped potato, with a measured layer of Gruyère for the gratin flavor.

Healthy Scalloped Potatoes with Gruyère and Thyme

Ingredients

Scale

2 1/2 pounds (1.1 kg) Yukon Gold potatoes
2 teaspoons butter, plus a little more for the dish
1 small yellow onion, finely chopped (about 3/4 cup)
2 garlic cloves, minced
2 cups (480 ml) 2 percent milk
1 tablespoon cornstarch
1 teaspoon fresh thyme leaves, or 1/2 teaspoon dried thyme
1 teaspoon fine sea salt
1/2 teaspoon black pepper
1/4 teaspoon freshly grated nutmeg
1/2 cup (50 g) finely grated Gruyère cheese
1 tablespoon grated Parmesan cheese
1 teaspoon chopped fresh chives or thyme leaves, to serve (optional)

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Instructions

Heat the oven to 375 degrees Fahrenheit (190 degrees Celsius) and butter a 2 quart baking dish, about 9 by 9 inches.
Slice the potatoes 1/8 inch (3 mm) thick on a mandoline or with a sharp knife. Soak the slices in cold water for 10 minutes, then drain well and pat dry.
Melt the butter in a medium saucepan over medium heat. Add the onion and cook until soft and translucent, 3 to 4 minutes. Stir in the garlic and cook 30 seconds more.
Pour in the milk and add the thyme, salt, pepper and nutmeg. Warm, stirring now and then, until the mixture steams and reaches a bare simmer, about 5 minutes. Do not let it boil.
Whisk the cornstarch with 2 tablespoons of cold water and stir the slurry into the milk. Cook 1 minute, until the sauce lightly coats a spoon, then remove from the heat.
Layer half the potato slices in the dish in tight overlapping rows. Pour over half the sauce and scatter half the Gruyère. Repeat with the remaining potatoes, sauce and Gruyère, then finish with the Parmesan.
Cover tightly with foil and bake for 45 minutes, until the center potatoes yield easily to the tip of a knife.
Remove the foil and bake 25 to 30 minutes more, until the top is deeply golden in spots and the sauce bubbles thickly at the edges.
Rest for 15 minutes so the sauce sets, scatter the chives or thyme over the top, and serve.

Author: Nora Ellis
Prep Time: 25 minutes
Cook Time: 1 hour 15 minutes