Ingredients:
- 3 lbs. potatoes, thinly sliced
- ½ onion, thinly sliced
- 9 Tbsp. all-purpose flour, divided
- 6 Tbsp. butter, diced and divided
- To taste salt and ground black pepper
- 3 cups whole milk, or as needed
Directions:
- Preheat oven to 375 F. Grease a 9-by-13-inch baking dish.
- Spread about 1/3 of the potato slices into the bottom of the prepared baking dish. Top with about 1/3 of the onion slices. Sprinkle 3 tablespoons of flour over the potato and onion. Arrange 2 tablespoons butter atop the flour. Season the entire layer with salt and pepper. Repeat layering twice more.
- Heat milk in a saucepan until warm. Pour enough warm milk over the mixture in the baking dish so the top of the liquid is level with the final layer of potatoes.
- Bake in preheated oven until potatoes are tender, 45 to 60 minutes.
