Creamy Leek and Potato Gratin with Jersey Milk

Preheat oven to 375°F (190°C). Grease a 9x13 inch baking dish with 1 tablespoon of butter.

Melt 2 tablespoons of butter in a large skillet over medium heat. Add the sliced leeks and cook, stirring occasionally, until softened and slightly caramelized, about 8-10 minutes. Add the minced garlic and cook for another minute until fragrant.

In a saucepan, heat the Jersey milk (and heavy cream, if using) over medium heat. Add the nutmeg, salt, and pepper. Bring to a simmer, then remove from heat.

Arrange a layer of potato slices on the bottom of the prepared baking dish, overlapping slightly. Sprinkle with some of the cooked leek mixture and thyme (if using).

Repeat layers of potatoes, leeks, and thyme until all ingredients are used, finishing with a layer of potatoes.

Pour the warm milk mixture over the potatoes, ensuring that they are mostly covered. Gently press down on the potatoes to help them absorb the milk.

Sprinkle the grated Gruyere cheese evenly over the top.

Dot the top with the remaining 1 tablespoon of butter.

Bake in the preheated oven for 45 minutes, or until the potatoes are tender and the top is golden brown and bubbly. If the top is browning too quickly, cover loosely with foil for the last 15 minutes of baking.

Let the gratin rest for 10-15 minutes before serving.