Crust for 8-inch Cake
1/4 cup graham cracker crumbs
1 teaspoon granulated sugar
1 tablespoon butter, melted

Crust for 9-inch Cake
3/4 cup graham cracker crumbs
2 tablespoons granulated sugar
2 tablespoons butter, melted

Filling for 8-inch Cake
8 ounces cream cheese, softened
1/4 cup granulated sugar
1 egg yolk
2 teaspoons vanilla extract
1 egg white (at room temperature)
1/3 cup sour cream
2 tablespoons granulated sugar

Filling for 9-inch Cake
1 1/2 pounds cream cheese, softened
3/4 cup granulated sugar
4 egg yolks
4 teaspoons vanilla extract
4 egg whites (at room temperature)
2 cups sour cream
1/3 cup granulated sugar

Preheat oven to 325 degrees F for an 8-inch cake or to 350 degrees F for a 9-inch cake.

In small bowl, combine crumbs, sugar and butter; blend well.

Butter sides of springform pan. Press crumb mixture into bottom of pan.

In a large bowl, beat cream cheese with an electric beater until light. Gradually add the sugar. Add egg yolks one at a time, beating well after each addition. Stir in 1/2 of the vanilla extract.

Beat egg whites until stiff peaks form in a medium-size bowl. Very gently fold egg whites into cream cheese mixture. Pour mixture over crumbs. Bake until set and lightly browned on top. Bake an 8-inch cake for 30 to 35 minutes. Bake a 9-inch cake for 1 hour. Let cake cool on wire rack for 15 minutes.

Turn oven up to 400 degrees F. Blend sour cream, and remaining sugar and the remaining vanilla extract in a medium-size bowl. Gently spread over top of cheesecake and bake until set, 5 to 7 minutes for an 8-inch cake or 10 minutes for a 9-inch cake. Cool to room temperature on wire rack. Chill at least 4 hours in the refrigerator.