Serves
8 servings
Ingredients
2 tablespoons unsalted butter, plus more greasing
1 medium yellow onion, chopped
1 garlic clove, minced
3 tablespoons all-purpose flour
2 cups whole milk
Kosher salt and freshly ground black pepper
2 1/2 pounds Yukon Gold potatoes, peeled and sliced into 1/8" thick
2 cups grated cheddar cheese, divided
Procedure
Preheat oven to 350°F and generously grease a 9 x13" casserole dish with unsalted butter.
To a medium skillet set over medium heat, add butter. When butter melts and foaming subsides, add onions and sauté, stirring often until tender, about 5 minutes. Add garlic and cook until fragrant, about 1 minute. Whisk in flour. Slowly pour in milk, whisking continuously. If sauce gets lumpy, continue whisking until smooth. Bring to boil and whisk until thickened, about 2 minutes. Season with salt and pepper.
Arrange potatoes into a thin, even layer into prepared casserole dish. Season with salt and pepper and sprinkle with 1/3 cup of cheese. Repeat layering with remaining potatoes and 2/3 cup cheese, seasoning each layer with salt and pepper. Pour milk mixture evenly over potatoes and sprinkle with remaining 1 cup cheese.
Cover dish with foil and transfer to oven. Bake until potatoes are fork-tender, about 50 minutes. Remove foil and bake until cheese is golden-brown, about 15 minutes.
To serve immediately: Remove from oven and cool slightly before serving.
