Preheat the oven to 325 degrees F. Press the cottage cheese through a sieve. In a large mixing bowl, cream the butter with the sugar, do not beat, then add the egg yolks and vanilla. Blend until the mixture is light and fluffy. Add the cream cheese, cottage cheese and cornstarch and blend well. In another mixing bowl, beat the egg whites until they form stiff peaks; then fold them into the cheese batter. Pour the mixture into the prepared crust and bake for about 1 hour or until the top is a golden brown. Leave the cake in the oven to cool for 2 hours then chill.