Preheat oven to 375 degrees F.
For making the crust, combine graham cracker crumbs, butter,and sugar and mix until combined.
Pour the crust mixture onto an ungreased 9-inch pie dish andpress the mixture to form a flat base layer.
Bake the crust for 7-8 minutes. Remove it from the oven.
Reduce the oven temperature to 350 F.
Now, prepare the filling by combining the cream cheese, sourcream, sugar, and cornstarch in a mixing bowl and mix until well combined. Add butter,vanilla extract and mix until smooth.
Pour the mixture over crust and bake for 30 minutes. Once baked, remove it from oven. Let it cool for 1 hour.
Mix the sour cream and powdered sugar until combined. Pour overthe cheesecake and chill or freeze until ready to serve.