Pies

Can she make a cherry pie, Billy Boy, Billy Boy?m Can she make a cherry pie, charming Billy?m

She sure can, Billy, and so can you. There's no excuse not to if you get a copy of Susan Purdy's new cookbook, ''Easy As Pie'' (Atheneum, $19.95 until Dec. 31; $22.95 after Jan. 1).

And you'll be baking more than cherry pie, too.

Three hundred and fifty recipes are included in this book - from apple to savory pies with fish, as well as galettes, quiches, pizza, turnovers, tartlets, and clafouti, a fruit tart with a thick pancake-like batter.

''My family and I tested all the pies at least once,'' says Mrs. Purdy. ''Of course we didn't eat all of them. We gave away a lot of pies to our neighbors with one wedge missing.''

But while the book title is catchy, isn't it really a misnomer?

''Not at all. Baking a pie is easy. Everyone's grandmother baked wonderful pies, along with everything else they had to do.''

So why do some people find pie-baking less than easy?

A lot of the problem seems to be the crust.

''Pastry inhibits some very good cooks,'' Mrs. Purdy says. ''I know two professional chefs who own restaurants in New York who won't bake a thing. Americans are fanatics about flaky pie crust.''

She lists four ways to avoid possible pitfalls:

* Make sure all ingredients and utensils are cold.

* Handle the dough as little as possible.

* Chill pie dough in pie pan for 30 minutes before baking. This will also reduce shrinking.

* Use a tablespoon of an acid such as white vinegar, lemon juice, or even orange juice as part of the total liquid ingredients. ''The acid is your insurance for a flaky crust. And you won't taste it,'' she insists.

Other hints she mentions are these:

* Use your fingers, not your palms when working dough. There's less heat in your fingers. A wire pastry blender or two forks are even better.

* Use all-purpose, not bread flour. Try to get a flour that is as low in gluten as possible.

* Pyrex or dull metal pie plates work better than shiny metal ones, as they tend to deflect heat.

* Use two-thirds butter and one-third margarine or lard rather than all butter.

''The French usually use all butter, which makes a tastier crust, but it's not as flaky,'' Mrs. Purdy explains.

She is especially keen on using a food processor when making pastry dough.

''It takes five minutes from flour to finished product with a food processor. And no matter what the manufacturer says,'' she emphasizes, ''don't process until a ball of dough is formed. That means you've overworked it. Use the pulse method and stop as soon as the dough begins to hold together.''

Using a few pulses of the processor before adding the liquid ingredients is also an easy way to do your sifting. Sifting, says Mrs. Purdy, is simply a way of mixing air into the flour.

''And watch the dough, not the directions,'' she advises. ''Maybe you don't need all of the five or six tablespoons of liquid called for in a recipe. Also, if you add an egg yolk, that's one tablespoon of liquid, and a tablespoon of acid is another - so you would use 2 tablespoons less of water.''

In researching her book, Mrs. Purdy discovered that there actually were four-and-twenty-blackbird pies!

''Can you imagine,'' she exclaims, ''back in the Tudor courts they would make 'animated pies.' Live birds were stuffed under a pastry crust at special banquets and holidays. The pies were then 'opened' in front of the guests and out would come a flock of live birds.''

For the coming holidays Mrs. Purdy recommends the following pies over the four-and-twenty-blackbird variety. Orange Pumpkin Pie 2 eggs 2 cups canned pumpkin, or fresh pumpkin cooked and mashed 1/2 to 3/4 cup granulated sugar, to taste 1 1/2 cups milk or cream (the heavier the cream the richer the pie) 2 tablespoons butter, melted 1/2 teaspoon salt 3/4 cup orange marmalade 1 tablespoon zest of orange 3/4 teaspoon cinnamon 1/2 teaspoon ground ginger 1/2 teaspoon ground nutmeg 1/8 teaspoon ground cloves

In an electric mixer or bowl, beat eggs. Add pumpkin and mix well. Beat in sugar, milk or cream, melted butter, salt, orange marmalade and zest, and spices.

Preheat oven to 425 degrees F. Partly bake a 10-inch basic pastry crust for 10 minutes with foil in crust filled with pie weights, rice, or beans. Remove weights and bake 8 minutes empty.

Remove pie shell from oven, let cool slightly, and reduce oven temperature to 400 degrees F.

Pour filling into pie shell. Set on baking sheet in center of preheated oven and bake for 40 to 50 minutes, or until the top is golden brown and a knife inserted into the custard 1 inch from the edge comes out clean. Do not overbake.

When knife comes clean at the custard's edge, pie is done even though the center may not yet be set. The internal heat of the pie will complete the baking out of the oven.

Cool pie on wire rack. Serve at room temperature.

Here is a cream topping Mrs. Purdy suggests for pumpkin pie. Ginger Cream Topping 1 cup heavy cream 1/2 teaspoon ground ginger, sifted 2 tablespoons confectioners' sugar, sifted 1 to 2 tablespoons candied ginger, minced fine

Whip cream to soft peaks, add ground ginger and sugar. Whip until stiff, then fold in minced candied ginger. Apple-Cranberry-Walnut Pie 5 to 6 medium-large Granny Smith, Cortland, or Greening apples, peeled and sliced 1 cup whole fresh or frozen cranberries 1/2 cup coarsely chopped walnuts 3/4 cup brown sugar, packed Juice of 1 large lemon 2 tablespoons flour 1/2 teaspoon nutmeg 1/2 teaspoon cinnamon 2 tablespoons butter, cut up 1 egg beaten with 1 tablespoon water for glaze Granulated sugar for topping (optional)

In a large bowl, toss fruit and nuts with sugar, lemon juice, flour, and spices.

Add mix to pastry-lined pan and dot with butter.

Brush egg glaze over edge of bottom crust.

Cover with top crust or make a lattice top with strips of pie dough.

Flute edge as desired, brush top with egg glaze, and sprinkle with sugar.

Set pie in lower third of oven preheated to 425 degrees F. and bake 10 to 12 minutes.

Reduce oven heat to 350 degrees F.

Move pie to center of oven and bake an additional 40 to 45 minutes, or until pastry is golden brown.

Cool on wire rack.

Serve warm with vanilla ice cream.