Sweet potatoes need only a little sugar and spice

Sweet potatoes and yams are as much a part of the holiday dinners as tiny pearl onions and cranberry sauce. Their inclusion is a tradition that dates back to ''Plimouth Plantation'' and the Pilgrim and Indian feast.

Actually, sweet potatoes as we know them had not yet been cultivated by the English colonies; what was served was a somewhat similar root vegetable called ''tuckah'' by the Indians.

Do not be confused by recipes that sometimes call for yams. The true yam is grown only in tropical areas.

What you see sold in the stores are really two or three varieties of sweet potato grown in this country. The yam has more sugar - and thus tastes more moist - but can be interchanged in most recipes calling for sweet potato.

Look for firm, uniformly shaped sweet potatoes, free of blemishes. Store in a cool, dry place and use within a few weeks.

The sweet potato and yam are both perfect foils for all sorts of sugar and spice embellishments, as well as coconut, marshmallows, pineapple, banana, and orange.

There are those who prefer their ''sweets'' in plainer form, also, so with them in mind, here are two not-too-sweet sweet potato dishes: Sweet Potato Souffle 2 pounds sweet potatoes or yams 1/2 teaspoon grated nutmeg 1/4 teaspoon salt 1/4 cup packed brown sugar 2 tablespoons butter or margarine 1/4 cup heavy cream 3 eggs, separated

Preheat oven to 400 degress F. Grease a 11/2-quart souffle dish or casserole. Cook sweet potatoes until tender, 20 to 30 minutes. Drain, peel, and mash. Add nutmeg, salt, sugar, and butter or margarine, and cream. Mix well. Stir in egg yolks thoroughly. Beat egg whites until stiff peaks form. Fold into potato mixture. Turn souffle mixture into prepared dish and bake for 35 minutes. Serves 6. Sweet Potato Pecan Puffs 2 1/2 cups mashed, cooked sweet potatoes 3 tablespoons butter or margarine, melted 1/2 cup sour cream 1/4 cup unsifted flour 1/2 teaspoon cinnamon 1/8 teaspoon allspice 1 1/2 cups coarsely chopped pecans 1 teaspoon salt

Place mashed sweet potatoes in large mixer bowl. Add remaining ingredients except pecans. Beat until smooth. Chill four hours. Preheat oven to 350 degrees F. Shape mixture into 11/2-inch balls. Roll in pecans. Place on lightly greased baking sheet. Bake 20 to 25 minutes, or until slightly firm to the touch. Sweet Potatoes Creole 8 cooked sweet potatoes 1 sliced lemon, with rind removed 3 sliced orange sections 1 1/2 cups crushed pineapple 2 1/4 cups pineapple juice 1 cup brown sugar 1/2 teaspoon salt 5 tablespoons butter or margarine

Peel sweet potatoes and cut into 4 lengthwise strips. Place alternate layers of sweet potatoes, lemon, orange, and pineapple in a greased casserole. Combine remaining ingredients and cook to a thick syrup. Pour syrup over potatoes. Bake in a 350 degree F. oven 30 to 40 minutes. Serves 8. Cranberry Sweet Potatoes 6 sweet potatoes, cooked or canned 1 1/2 cups whole cranberry sauce 3/4 cup water 1/2 cup brown sugar 3/4 teaspoon grated orange rind 3/4 teaspoon ground cinnamon 1 1/2 tablespoons butter or margarine

Arrange sweet potato halves in baking dish. Mix cranberry sauce, water, sugar , orange rind, and cinnamon. Cook, uncovered, 5 minutes. Add butter or margarine. Pour over potatoes and bake uncovered at 350 degrees F. for 20 minutes, or until glazed and hot. Serves 6. Cider and Maple Sweet Potatoes 6 medium sweet potatoes 1/2 cup maple syrup 1 tablespoon butter 1 teaspoon salt 1 cup apple cider 1/2 cup water

Boil potatoes in jackets until nearly tender. Peel and slice into baking dish. Heat remaining ingredients to boiling. Pour over potatoes and bake in 300 degree F. oven for 1 hour. Serves 6. Applesauce Sweet Potato Casserole 6 medium sweet potatoes 3/4 cup applesauce 1/4 cup butter or margarine, softened 1/2 teaspoon finely shredded lemon peel 1/2 teaspoon salt 2 egg yolks 2 stiffly beaten egg whites

In large saucepan, cook sweet potatoes, covered, in enough boiling salted water to cover for 30 to 40 minutes, or until tender. Drain. Peel potatoes. Mash on low speed of electric mixer. Add applesauce, butter or margarine, lemon peel, and salt. Beat until fluffy. Add yolks. Beat well. Carefully fold stiffly beaten egg whites into potato mixture. Turn into a buttered 11/2-quart casserole. Bake, covered, in a 350 degree F. oven for 20 minutes. Uncover and bake 25 minutes. Serves 8 to 10.