Salted butter, for the baking dish
3 c. whole milk
1 1/2 c. heavy cream
4 lb. Yukon Gold potatoes (about 7 medium), peeled and sliced into 1/8-inch thick rounds
1 tbsp. fresh thyme
3 garlic cloves, minced
1/8 tsp. ground nutmeg
2 1/2 tsp. kosher salt
1/2 tsp. black pepper
12 oz. white cheddar cheese, shredded
Chopped fresh chives, for garnish
Step 1 Preheat the oven to 375˚. Butter a 4-quart baking dish. Combine the milk, heavy cream, potatoes, thyme, garlic, nutmeg, salt and pepper in a large pot. Bring to a boil over medium-high heat, then reduce the heat to medium and simmer, stirring occasionally, until the potatoes are slightly tender, about 3 minutes.
Remove from the heat.
Step 2 Spoon one-third of the potato mixture into the prepared baking dish and sprinkle with one-third of the cheese. Repeat to make another layer of potatoes and cheese, then spoon the remaining potato mixture and any remaining heavy cream from the pot over the top. Reserve the remaining cheese for later.
Step 3 Cover the baking dish tightly with foil and bake until the potatoes are tender and the cream mixture is bubbly all over, about 40 minutes.
Step 4 Remove the foil and switch the oven to broil. Top the potatoes with the reserved cheese and broil until bubbly and golden, 3 to 5 more minutes. Let sit for 30 minutes before serving. Garnish with chives.
