Step 1

Heat the oven to 375°F with a rack in the middle position. In a 1-quart baking dish, shingle in the potato slices; they will be tightly packed.

Step 2

In a saucepan, combine the cream, mustard, nutmeg, 1 teaspoon salt, ⅛ teaspoon pepper and bay (if using). Bring to a simmer over medium, stirring, then immediately pour over the potatoes. Cover tightly with foil and set on a rimmed baking sheet to catch bubble-overs. Bake until the tip of a knife inserted into the potatoes meets just a little resistance, 40 to 45 minutes.

Step 3

Remove from the oven and uncover the baking dish. Sprinkle the Parmesan evenly over the surface. Bake, uncovered, until golden brown, another 20 to 25 minutes. Cool on a wire rack for about 20 minutes before serving.

Step 4

To serve 6 to 8: Follow the recipe using 2 pounds Yukon Gold potatoes, 2 cups heavy cream, 1½ teaspoons Dijon mustard, ¼ teaspoon nutmeg, 2 teaspoons kosher salt, ¼ teaspoon black pepper, 2 bay leaves or thyme sprigs (optional) and 2 ounces (1 cup) finely grated Parmesan or Asiago cheese. Use a 1½-quart baking dish (such as an 8-inch square baking dish) and increase the covered baking time to 50 to 60 minutes.

Step 5

To serve 10 to 12: Follow the recipe using 3 pounds Yukon Gold potatoes, 3 cups heavy cream, 2¼ teaspoons Dijon mustard, ⅜ teaspoon nutmeg, 1 tablespoon kosher salt, ⅜ teaspoon black pepper, 3 bay leaves or thyme sprigs (optional) and 3 ounces (1½ cups) finely grated Parmesan or Asiago cheese. Use a 3-quart baking dish (such as a 9-by-13-inch baking dish) and increase the covered baking time to 50 to 60 minutes.