Combine crust ingredients and pat into bottom and sides of pan. Beat cream cheese thoroughly; add sugar gradually; add eggs in thirds; add vanilla; pour into prepared pan. Bake at 375 for 25 minutes; remove from oven and add topping. To prepare topping, whip sour cream; add sugar and vanilla, and pour over cake. continue baking at 500 for 5 minutes. Important chill at LEAST 24 hours.