- 2 tablespoons butter plus more for baking dish
- 1 cup finely chopped leeks (if needed, sweet onion may be substituted)
- 2 cloves garlic, grated/minced
- 1 teaspoon dried thyme
- 1 cup whole milk
- 1 cup heavy cream
- 2 teaspoons kosher salt
- 1/2 teaspoon ground black pepper
- 2 1/2 pounds yellow/golden potatoes, peeled and sliced thin
- Preheat the oven to 350-degrees F. Coat an 8×8-inch (or approximate) baking dish with butter.
- Heat a medium saucepan over medium-high heat. Add butter. When butter has melted, add leeks; cook, stirring for 2 minutes.
- Add garlic, thyme, continue to cook, stirring for 30 seconds.
- Stir in milk, heavy cream, salt, and pepper. Bring to a boil, lower heat to a simmer, cook, stirring occasionally, until mixture has slightly thickened, about 5 minutes.
- Add potatoes; stir to coat potatoes. Transfer mixture to prepared dish, spreading potatoes evenly in dish.
- Bake until potatoes are done, lightly brown and bubbly, about 1 hour. If time permits, baste potatoes with sauce halfway through cooking. Let cool slightly before serving.