Sweet Potatoes or Yams?: That Is the Question : Roots, tubers: Many cooks use them interchangeably but they stem from different families.

There is an annual debate in many American homes as to whether the orange, potato-like vegetable that’s traditional on our tables at this time of year is a yam or a sweet potato.

On one hand there are those copper-colored things, a bit elongated and often irregularly shaped, with a moist, almost oily flesh that sometimes oozes a sweetish liquid when baked. I always assumed these were yams, but they’re not. And they’re usually sold as yams, which adds to the confusion.

Then there’s the cream-colored variety that looks more like a pinkish-yellow potato. Its flesh is drier, more like a white potato and mealier than the copper-colored variety. I thought this was a sweet potato.

In fact, both of them are. We rarely see real yams in this country.

Both varieties of sweet potato are true roots of a plant of the morning-glory family and are North American natives. Real yams, on the other hand, are tubers (swollen roots) and are tropical relatives of the lily. By the way, white potatoes, which are not roots at all but technically the swollen tips of underground stems, belong to the tobacco family. (Most of us do have skeletons in our genealogical closets.)

Many cooks use the two varieties of sweet potatoes interchangeably, and for many recipes, especially the mashed ones, it makes little difference which variety you use. Both are equally flavorful in sweet-potato soup or when boiled and tossed in butter and parsley.

If you like light, airy mashed potatoes, use the yellow variety--the result will be fluffier. (I always use milk, not cream, in mashed potatoes, whether they’re sweet or white.) They are also preferred in the hash recipe that follows. These yellow spuds stick together better, and the patties soak up less oil during cooking.

The copper-colored potatoes are better in sweet-potato pie because their texture is denser, smoother and less starchy. I also prefer them in that ubiquitous casserole . . . you know, the one laced with marshmallows.

In some cases, the age of the potato and the amount of water in the flesh determine its use. In October, when the potatoes are freshly dug (the season extends through March), both varieties have a higher water and sugar content and their flesh is less compact than later in the season.

The longer they are stored, the more compact their texture becomes as the sugar turns to starch and the water evaporates. Use older potatoes of both varieties to make gratins and scalloped-potato dishes. Or use them to make sweet-potato salad. They are easily as good as new potatoes for soup making.

Meal providers should also know that sweet potatoes are a good source of vitamins A and C and the mineral potassium. Boiled or baked, they have about 165 calories apiece.

SWEET POTATO AND HAM HASH

1 medium sweet potato, about 1 pound

1 pound ham

1 teaspoon salt

1/2 teaspoon ground white pepper

4 to 6 tablespoons butter or margarine

8 poached eggs

1/4 cup sour cream

Wash but don’t peel sweet potato and shred on fine blade of shredder or food processor. Place in mixing bowl and set aside.

Finely chop ham and pulse, using metal blade of food processor. Add ham along with salt and white pepper to sweet potato and mix well.

Heat 1 tablespoon butter in non-stick 6-inch skillet over medium heat and add 1/4 potato-ham mixture. Cook about 4 minutes, pressing down gently to compact hash as it cooks. Flip patty and cook another 5 minutes. Add more butter and repeat with remaining mixture, adding butter to skillet as needed.

As each hash patty is done, transfer to oven-proof dish and place in 250-degree oven to keep warm. To serve, place 2 poached eggs on each serving hash and garnish each with dollop sour cream. Makes 4 servings.

PUREE OF SWEET POTATO SOUP

1 tablespoon oil

1 medium onion, chopped

6 cups canned low-sodium chicken broth, water or a mixture

1 1/4 pounds sweet potatoes, peeled and coarsely diced, about 3 cups

1/2 teaspoon ground nutmeg

1 teaspoon salt or to taste

1/4 teaspoon white pepper

1/2 cup chunky cranberry sauce

Sour cream

Heat oil in pan over medium heat and add onion. Cook, stirring, 5 minutes. Add chicken broth, sweet potatoes, nutmeg, salt and white pepper. Increase heat to high. Cover and bring to boil. Reduce heat to low and simmer, uncovered, 30 minutes. Remove from heat and puree soup in processor in batches.

Return pureed soup to pan and reheat, covered, over low heat. To serve, place dollop cranberry sauce and sour cream in bottom of each soup bowl. Transfer hot soup to tureen or pitcher and ladle into bowls at the table. Makes 5 to 6 servings.