The ingredient that differentiates a pavlova shell from a classic meringue -- corn flour -- also makes it more conducive to freezing. Both meringues and pavlova shells contain the same primary ingredients -- egg whites and sugar. But corn flour, which gives the pavlova shell its marshmallow-like interior consistency, prevents the crisp edges of the shell from softening upon thawing, like classic meringues do. When they're thawed, pavlova shells maintain their structure, so you can add the classic filling ingredients -- whipped cream and soft fruits -- in the last few minutes before serving.
Bake the pavlova shell on a baking sheet lined with parchment paper for 1 hour at 300 degrees Fahrenheit, then turn the heat off.
Open the oven door slightly and let the pavlova shell cool down in tandem with the oven until it reaches room temperature, after about one hour. Use a folded towel to hold the door open, if necessary
Transfer the baking sheet from the oven to the freezer. If your freezer isn't large enough to hold the pan, transfer the pavlova to a plate -- without taking it off the parchment paper.
Freeze the pavlova shell until it is firm throughout, about 1 to 1 1/2 hours.
Take the pavlova shell out of the freezer and carefully wrap it in freezer paper. Place it in a heavy-duty freezer bag, and mark the date on the bag. Use within one month for best results.
Thaw the pavlova meringue at room temperature for two hours before serving time. Assemble the pavlova a la minute, or as close as possible to serving time.