February 18, 2014 - Radio Kitchen - Scalloped Potatoes
There's no denying that this is the season of hearty eating, and along with our big old rib roasts and roasted chickens, there has to be something else on the plate. And few dishes say "hearty" as well as a nice steaming casserole of scalloped potatoes.
Then name "scalloped" refers to the technique of cooking in milk. There are no sea scallops involved.
This is just one of very many dishes that are grouped under the category of gratins. Essentially, a gratin is a vegetable-based dish that is topped with a golden brown crust made up of breadcrumbs, cheese, eggs or butter. That gives us a lot of latitude.
The dish we call Scalloped Potatoes is a classic gratin. Basically, this is a casserole of thinly sliced potatoes cooked in its own creamy sauce, topped with a cheesy crust, traditionally served in its own shallow baking dish. That's the basic idea, but there a dozens of variations.
First some basics: the choice of potato makes a difference. An Idaho baking potato, sliced thin and pre-cooked will absorb a lot of liquid, making it softer, but also more prone to breaking up. A firm, waxy potato like a red keeps its shape and stays firm, but some might say, it's too firm. A good compromise would be the Yukon Gold, which has qualities of both. In the end you want a soft, fully cooked slice of potato that has kept its shape. The potatoes should be sliced to a consistent thickness, thus a mandolin is the ideal tool. We think a thin 1/8" slice is ideal. To test, pinch a slice, and it should be able to bend but not break.
To pre-cook the potatoes or not is the big question. Parboiling insures that the potatoes will be tender, not stiff and raw tasting...but parboiling removes a lot of the starch that the dish depends on. Here's a compromise: pre-cook your sliced potatoes in milk or cream, then use that milk to make the sauce for the dish. After a few minutes of gentle cooking, the milk takes on the starch and becomes quite creamy.
The sauce that will be the salient feature of the dish is usually a simple béchamel (butter, flour, cream, salt and pepper), mixed in with some seated onions and your choice of seasonings. Mix up a lot of it.
After pre-cooking the potatoes, you then assemble them in your shall baking dish. Keep that big bowl of your simple oniony béchamel sauce handy. Spread the potato slices and their sauce in layers, adding a little more sauce (and some gated cheese if you like) to cover each layer. Keep building them up until you have used up all your potatoes. Pour enough béchamel over the dish to ensure it is thoroughly coated. Do not stack a bunch of slices together. They will not cook properly and you will have a stiff texture.
Cheese for the topping is a matter of taste, but the main choices are parmesan, cheddar or gruyere. Whichever you use, grate it coarsely, and be generous as you sprinkle it on. Working some breadcrumbs into the topping is totally permissible.
Baking should be a long, slow affair. We prefer a moderate oven and about 45 minutes baking time. The goal is to have the potato slices surrender their starch to the cream sauce, and enhance its texture. If you do not pre-cook your potatoes, then you need at least an hour in that low to moderate oven. And of course, there is nothing wrong with adding more cheese at the end, and popping the dish under the broiler for a few seconds.
Now for the variations. The most common elaboration is ham, and in this case I argue that the more tender type of ordinary cooked ham is best. Tougher styles like Virginia Country ham or prosciutto don't match up well with the overall goal of total creamy texture. So my mother's approach of using nice plump chunks of ham scattered throughout the dish seems perfect.
And of course there are many vegetables that can make an appearance. Topping my list would be thick slices of onion, broccoli florets, cooked spinach or thinly sliced sautéed mushrooms.
Scalloped potatoes are a lot of work, even with a mandolin, and the recipes, although seemingly simple, can be tricky. But once you learn how to nail it, you can look forward to many, many dinners made ever so comforting by this most comforting of side dishes.