FOOD 101: Scalloped potatoes, an American classic

Our grandmothers’ grandmothers knew scalloped potatoes deep in their bones. Plain or fancy, depending on the occasion, it was a popular go-along with roasts and chops on the farm or in the city. Arranged in layers and smothered in liquid, the potatoes were baked under a blanket of toasty bread crumbs. They still make a celebration of the Sunday roast or chops at a midweek supper. They improve with cheese tucked in between the layers. 

The original idea derived from French country cooks who kept the house warm, traditionally baking their potatoes in an oval pottery dish, called a gratin. The description of a gratin spreads its arms out wide to embrace any vegetable under a crust of bread crumbs and/or cheese. But the French, being French, often call the non-starchy version a tian. Filled with peppers, eggplant or tomatoes rather than potatoes, it is often baked in an oval made of copper.

I searched a dozen cookbooks for a definite recipe. I’ve “scalloped” so many potatoes, but I stopped using a recipe after the first. It was so much fun to just play with the ingredients. 

My cookbook stash provided some guidance passing along the instructions. Make that “guidelines” because once started, a cook can spend a lifetime riffing on the basics.

So, here’s the cast of characters with all their quirks: 

Buttered casserole dish. Thick pottery, stainless steel or heavy copper, oval or rectangular. Swipe the insides with a clove of garlic, if you must. I don’t. Plain cooking at its best demands the cook use restraint. 

Potatoes. Choose Idaho or Yukon gold. Idaho potatoes (russet potatoes grown in rich Idaho soil) give a gutsy, warm flavor. Yukon golds’ color and smooth texture suggest butteriness. Sliced thinly — crosswise into rounds or lengthwise — both shapes shingle easily into the bottom of a baking pan to settle on top of one another in layers. Set the sliced potatoes aside in a bowl of cold water to cover to keep them from discoloring until ready to use. 

Onions. Sweet, not sharp. Just a suggestion, about half a small onion, very thinly sliced. I skip them if I feel they might overwhelm the potatoes.

Wet ingredients. Choose from chicken stock, vegetable stock, whole milk, cream or half-and-half. Each one adds its own level of richness. Some flour whisked into the liquid thickens it. Some cooks use a béchamel sauce, but I think all that melting and whisking and de-lumping adds extra steps.

Cheese. The most basic recipe doesn’t need cheese, but I can’t resist that extra flavor and gooeyness. Forget the orange cheddar because of the dayglo color that looks worse when cooked (except in a grilled cheese sandwich). Don’t bother with blue cheese. You never know which kinds might react to heat and start to smell like a locker room. Stick to good old American cheddar. Or Gouda. Or Swiss. Very thinly sliced to order at the deli counter — they save the cook a lot or work. Tuck the sliced cheese between the layers of potato in the casserole dish. Or grate a mixture together and scatter it between the layers.

Breadcrumbs. Fresh white breadcrumbs. I save up the ends of bread loaves and other bread products — stray English muffins or biscuits, the last bagel or dinner roll, even a plain donut — in a plastic bag in the freezer. When I get enough, I grind them in the food processor and return to the freezer so there’s always a cache of fluffy breadcrumbs on hand. I add seasonings and fresh or dried herbs to match the recipe. 

Butter. Using unsalted butter for cooking gives the cook complete control of the flavor. Drizzle the butter over the top of the potato layers for a crunchy crust.

SCALLOPED POTATOES

Makes 6 to 8 servings

1 tablespoon unsalted butter

3/4 cup fresh bread crumbs

2 tablespoons all-purpose flour

1 1/2 teaspoons dried thyme

1 1/2 teaspoons salt

1 teaspoon ground black pepper

2 3/4 russet (Idaho) potatoes, peeled and thinly sliced

1/2 small onion, sliced thinly, rings separated

1 1/2 cups chicken stock

3/4 cup half-and-half

1 tablespoon Dijon-style mustard, optional

1. Butter a 9-inch-x-13-inch baking dish. Preheat the oven to 400F.
2. Melt the butter in a small skillet over medium heat. Add the breadcrumbs and cook, stirring, until golden. Set aside.
3. Whisk together the flour, thyme, salt and pepper. Layer a third of the potatoes then a third of the seasoned flour and half of the onions. Repeat, ending with potatoes.
4. Whisk together the stock, cream and mustard, if using. Pour this evenly, nearly to the top, over the potatoes. Bake for 25 minutes. Remove from the oven. Scatter breadcrumbs over the top. Return to the oven for an hour longer. The top will be brown, the potatoes tender when pierced, and the liquid mostly absorbed but bubbling lightly around the edges of the potatoes. 
5. Let this rest for 10 to 15 minutes for easier cutting.

Linda Bassett, a Marblehead resident, has worked as a cook, trained up-and-coming chefs, studied food history and led food tours. Her book,“From Apple Pie to Pad Thai,” is about local cooks and cooking.