Tom Burford, "Professor Apple" to his friends, has some advice for bakers torn between using tart or sweet varieties to make an apple dessert: Use both. In fact, toss in a third, a sweet-tart combination, for a fuller flavor.

Apples are Burford's passion. If his mother hadn't made it back to the house on time on a hot August day 70 years ago, he might have been born under an apple tree. Until 1995, he owned and operated a nursery outside Lynchburg, Va., where he grew both heirloom apples and modern varieties. He is now an orchard and nursery consultant, author and apple historian. (He'll lead a tasting Saturday at Monticello of apple varieties from the Jefferson era. For more information and reservations, see www.monticello.org.)

Decades before the folks at Cooks Illustrated concluded that two kinds of apples are twice as good as one in making the ideal apple pie, Burford was using three. His mother did it, and so did her mother. "For an exceptional pie, there should be a mixture of apples," Burford says, "not just Granny Smith, for goodness' sake."

When blending different varieties of apples -- long the practice in making cider and juices -- Burford looks for tartness and sweetness, then supplements those apples with a third type that has both. The degree of ripeness affects the balance as well.

Over the years, he has experimented with countless combinations from among the 400 apple varieties in his nursery. "It may be different every time," he says, "but it's always good, that's the thing about it."

One seeming problem in using more than one type of apple in a baked dessert is that one variety might cook faster and turn mushy while others are still firm. No problem, says Burford. "The Golden Delicious will cook down most, and that's good because it becomes sort of the bonding agent for the rest of the apples," he says.

When Burford bakes, the flavor comes from the apples. Period. Because he is mixing apple varieties, there's no added sugar in his fillings, nor cinnamon, nutmeg or spices of any kind. Lemon juice? Perish the thought. Leaving out all those distracting flavors, he says, "allows the palate to taste the apples, and not the support system."

What about serving apple pie with a slice of cheddar or a scoop of vanilla ice cream? There's a long pause on the other end of the phone. Suffice to say, save them for another use.

Simple Apple Crisp

6 to 8 servings

This is Tom Burford's favorite combination. The Golden Delicious contributes sweetness, so there's no need for sugar in the filling. The Winesap is tart; hence, no lemon juice. The Jonathan is both sweet and tart, for added depth of flavor. Taken together, this crisp is slightly tart. Any or all of these apple varieties can be substituted; consult "Look for a Balance" to make selections.

Based on a traditional Virginia mountain recipe.

6 apples: 2 Golden Delicious, 2 Winesap and 2 Jonathan, peeled, cored and sliced into eighths

4 ounces (1 stick) unsalted butter, softened

1 cup flour

1 cup sugar

2 to 4 tablespoons apple cider or hard cider (optional)

Preheat the oven to 325 degrees. Have ready an ungreased 8- or 9-inch-square baking pan.

Mix the apples together in a medium bowl and transfer them to the pan.

In a medium bowl, using a whisk, combine the butter, flour and sugar until the mixture resembles coarse meal. Sprinkle it over the apples.

Bake for 50 to 60 minutes or until golden brown and bubbly. Halfway through the cooking, if the apples look a little dry, add 2 to 4 tablespoons of cider. Let cool slightly before serving, or serve cold.

Per serving (based on 8): 312 calories, 2 g protein, 52 g carbohydrates, 12 g fat, 31 mg cholesterol, 7 g saturated fat, 2 mg sodium, 3 g dietary fiber

Recipe tested by Marcia Kramer; e-mail questions to food@washpost.com