Peaches and berries with a crunchy topping

This combination of peaches and berries is baked with cinnamon sugar and the crispest, crunchiest topping ever. It can be served immediately while it is piping hot and is so good you can't wait for it to cool even if it burns your tongue, or it can be served at room temperature or refrigerated and it will be just as wonderful.

Try it topped with a scoop of vanilla ice cream. The recipe comes from Maida Heatter's ''New Book of Great Desserts'', (Knopf, $17.50) Peach and Blueberry Casserole 1 pint fresh blueberries 2 pounds (6 or 7 medium) ripe peaches 3/4 cup plus 3 tablespoons granulated sugar 1 cup sifted all-purpose flour 1 teaspoon baking powder 1/2 teaspoon salt 1 egg 51/3 tablespoons unsalted butter, melted 1 teaspoon cinnamon Adjust rack one-third down from top of oven and preheat to 375 degrees F. Generously butter a 9 by 12-inch pan or 2-quart casserole.

Wash and drain berries and set aside. Peel peaches and slice each into 6 to 8 wedges. Place peaches in casserole. Cover with berries. Sprinkle with 2 tablespoons sugar. Set aside.

In mixing bowl sift together flour, 3/4 cup sugar, baking powder, and salt. Add unbeaten egg. With fork stir mixture. When it is partially mixed, exchange fork for pastry blender and chop until most of dry ingredients are coarsely blended, just to incorporate dry ingredients.

With large spoon, sprinkle topping evenly over berries. Drizzle melted butter over topping. Mix cinnamon with remaining tablespoon of sugar and sprinkle over top. Bake uncovered for 15 minutes. Then increase temperature to 400 degrees F. and bake 12 to 15 minutes more until topping is lightly browned.

Note: This can be prepared hours ahead. Refrigerate it, and then let it stand at room temperature for about half an hour, and bake it while you are having dinner.