4heaping cups peeled and thinly sliced potatoesabout 2 pounds
1/4teaspoonground black pepper
Prep: Heat the oven to 375°F and butter a 2 quart casserole dish.
Sauté the sliced onions until softened and starting to brown.
Layer the casserole: Layer half of the sliced potatoes in the casserole dish and top with all of the onions and half of the sliced butter, then arrange the remaining potatoes on top. Whisk together all ingredients for the sauce in a saucepan, then gently heat on the stove just before boiling, then pour evenly over the casserole (it should just cover the potatoes, if there isn't enough sauce, pour a little extra milk on top).
Bake: Bake the potatoes for 20 minutes, then loosely cover with aluminum foil and finish baking for 20-25 minutes, or until the potatoes are cooked through and the sauce is bubbly. Let sit on a rack on the counter for 5-10 minutes before serving so the sauce can thicken.
Step by Step Images:
Sauté the onions until they're softened and starting to brown and caramelize for the best flavors.Make sure to slice the butter thinly to be able to spread it across the casserole dish.Once the potatoes, onions and butter are layered in the casserole dish, carefully pour the warmed sauce over the dish so that the potatoes are just covered. Add some additional milk (cold is fine here) if it seems too dry.
potatoes: Use starchy potatoes because they turn out nice and creamy, and they are a vital part of thickening the sauce. Russets work and will turn out extremely creamy, Yukon Gold are so versatile and work perfectly here, too. They hold their shape a little better.
milk: I use whole milk for the richest and creamiest results, but you can use a lower fat percentage if you prefer. You can also use part cream and part milk, or all cream for a very rich dish.
butter: don't skimp on the butter, scalloped potato occasions are not the time and place to go on a diet.
Slicing the potatoes: Slicing the potatoes with a mandolin or a food processor is much easier and faster than doing it by hand. If you don't have those, use a large, sharp knife and a sturdy chopping board to make the slicing easy and efficient.Why warm the sauce: I warm the sauce ingredients before adding them to the casserole so that the baking process is quick-started. Don't worry, your sauce doesn't have to thicken yet on the stove, and it doesn't need to boil either - just heat it up until it's steaming hot, then VERY carefully pour it over the potatoes.