The sweet potato is an often-neglected spud, regularly pushed out of the culinary limelight by mashed potatoes, its renown not even close to that of the famous french fry.

The sweet potato did not help its reputation when, for prior years, it regularly showed up at the supper table, tarted up, dotted with marshmallows and calling itself "candied." There was also the problem of being orange, not a fetching color.

Despite these limitations, the sweet potato is, I think, a food this fella could fall for.

The sweet potato happens to be a favorite of Deborah Madison. She is a founding chef of Greens restaurant in San Francisco and the prize-winning author of nine cookbooks, including Vegetarian Cooking for Everyone, a work often called "the vegetarian bible." Madison calls herself a "vegophile" - that is, someone who loves to cook vegetables most of the time, but also cooks fish, an occasional rib-eye or a roast chicken.

I telephoned Madison at her home in Galisteo, N.M., to talk about tubers. She immediately referred me to the two-page spread in her 2002 cookbook, Local Flavors, that detailed six different sweet-potato varieties - Kotobuki, Hanna, Garnet, Diana, Jewel and Beauregard.

The light-colored flesh of the Kotobuki sweet potatoes tastes like chestnuts, she said. Generally speaking, she said, the darker the flesh, the sweeter the potato. Sweet potatoes are sometimes mistakenly called yams. Real yams, she said, are a tropical vegetable that grows in Asia and West Africa. A good way to cook sweet potatoes of any hue, she said, is to wrap them in foil and roast them either in a wood fire or in charcoal briquettes. Roasting, she said, caramelizes the sugar in the sweet potatoes.

A simpler treatment, she said is to cook sweet potatoes in a pressure cooker and serve them with some fresh goat cheese. "The fresh goat cheese has a tang that stands up to the sweetness of the potatoes," she said.

Sweet potatoes are loaded with vitamin C, iron and calcium. Many of the recipes in Madison's books call for a simple, straightforward treatment of vegetables.

Yet the sweet-potato gratin I was drawn to in the recently released paperback version of her Vegetarian Suppers From Deborah Madison's Kitchen called for baking sliced sweet potatoes with cheese and a cup of cream.

"I do love that dish," Madison said, adding that she "has a soft spot for gratins."

She said, "Part of what makes a supper appealing is that people are comfortable with the food. And people are comfortable with gratins," she said.

When making this gratin, Madison told me, you have to use cream or half-and-half. You can't try to backslide into virtue by substituting milk.

"You need a certain amount of fat," she said of her call for cream. "I guess you could use milk and add flour. But that would get in the way of the clear flavors." Never needing an excuse to cozy up to cream, I embraced this recipe.

I followed Madison's advice and bought sweet potatoes from a farmer. I got mine from Bob Knopp Jr., who sells sweet potatoes and other produce grown on his Anne Arundel County farm at the Sunday morning farmers' market in downtown Baltimore.

"A farmers' market is where you will find the best food anywhere," Madison wrote in Vegetarian Suppers. "So there is less you have to do to make it taste good. It is good already."

One night when I got home from work, I pulled out Knopp's sweet potatoes - they were Beauregards - peeled and sliced them and dropped the slices into a pot of boiling water. They did not stay long in the boiling water, just long enough to get tender.

A few minutes later, I mixed the tenderized potatoes with some sauteed onions and fresh sage. I skipped the parsley that the recipe called for because I didn't have any. I tossed these ingredients and a minced clove of garlic together in a bowl. Then I scooped up about one-third of the mixture in the bowl, and spread it in a lightly oiled baking dish.

I sprinkled grated cheeses on top of the potato layer, then repeated the procedure until the dish was full.

Next I poured in the cream, a cup of it, warmed slightly in the microwave.

The gratin baked in a 350-degree oven for about 40 minutes. For the first 25 minutes, the dish was covered with foil. Then the foil came off and I cooked it for another 15 minutes or so, until the gratin had browned.

I let it cool off for a few minutes, then spooned up servings. It was a glorious, rich mixture, with the natural sweetness of the potatoes, being "brought down to earth" as Madison later described it, by the nutty flavor of the cheese.

This dish made me much fonder of sweet potatoes. It almost made me forget the tuber's marshmallow-laden past.

rob.kasper@baltsun.com

Sweet-Potato Gratin With Onions and Sage

-- Serves 4

2 teaspoons oil plus a little for cooking dish

1 large onion, chopped into 1/2 -inch dice

2 tablespoons chopped fresh sage or 2 teaspoons dried

3 medium sweet potatoes (about 1 1/2 pounds), thinly sliced

1 large handful of fresh parsley leaves, chopped

1 plump garlic clove, finely chopped

sea salt and freshly ground black pepper to taste

3/4 cup grated Gruyere or smoked mozzarella cheese (divided use)

1 to 2 tablespoons grated parmesan cheese (divided use)

1 cup cream or half-and-half, warmed (milk won't work)

Preheat oven to 350 degrees. Lightly oil a 2-quart gratin dish and put a moderately large pot of water on to boil.

Put 2 teaspoons of oil in a skillet over medium heat and add the onion and sage. Cook, giving them an occasional stir, until soft and golden, about 12 minutes.

Meanwhile peel the sweet potatoes, then slice them as thinly as you can manage. Salt the water, then drop them in. Allow the water to return to a boil, which may take a few minutes. Boil for a minute or until the potatoes are partly tender when pierced with a knife, then drain. Toss them with the onions, chopped parsley and garlic.

Scoop a third of the potato mixture into the prepared gratin dish and even the potatoes out. Season with salt and pepper. Add half the Gruyere and grate a little parmesan over the mixture. Repeat making one or two more layers, covering the last with a dusting of parmesan.

Pour the warm cream over all. Cover with foil and bake in the center of the oven for 25 minutes. Remove the foil and continue baking until the potatoes are soft and the gratin has browned, another 25 minutes of so. Let the gratin stand a few minutes before serving.

From "Vegetarian Suppers From Deborah Madison's Kitchen"

Per serving: 286 calories, 11 grams protein, 16 grams fat, 9 grams saturated fat, 25 grams carbohydrate, 4 grams fiber, 46 milligrams cholesterol, 152 milligrams sodium