If you have any extra cheesecake mixture left over after filling the pie pan (I always do), put it in a pastry bag or heavy-duty plastic bag and put it in your freezer for about 7 to 10 minutes, just to firm it up a bit to the thickness of whipped cream. Then take it out and decorate the top of the Key Lime Cheesecake. (If it is in a plastic bag, snip the corner off.)