8 cups peeled and diced russet potatoes, 2-inch chunks
2 teaspoons salt
¼ teaspoon ground black pepper
2 cups shredded cheddar cheese
2 cups milk
1 cup cream
3 egg yolks
Pinch nutmeg
½ cup grated Parmesan cheese
Preheat the oven to 375 degrees Fahrenheit. Butter a 9-by-13-inch casserole dish and set aside.
Toss the potatoes with the salt and pepper.
Place one-third of the potatoes in the prepared casserole dish. Sprinkle with one-third of the cheddar cheese. Repeat layers until all the potatoes and cheese are used.
Heat the milk in a small saucepan over medium heat until simmering.
While the milk is heating, whisk the cream and egg yolks together in a small bowl.
Remove the milk from heat. To temper the cream mixture, add one ladle of the hot milk to the cream mixture and stir to combine.
Slowly add the cream mixture to the milk while stirring with a whisk. Add nutmeg and mix well.
Pour the milk mixture over the layered potatoes.
Cover with aluminum foil and bake for 1 hour, 20 minutes, until the potatoes are tender.
Remove the foil, top with the Parmesan cheese, and bake uncovered until the cheese is melted, about 5 additional minutes.