Fill a saucepan with about 2-3 inches of water. Bring to a boil. Find a bowl that will fit on top of the pan without touching the water. (I like to use a glass bowl over a 2 Qt. saucepan.)
Whisk the egg whites and the sugar in the bowl. Place it over the boiling water and whisk until the mixture reaches 120-160º. This takes just a few minutes. You can use a candy thermometer if you have one, or even a (clean) meat thermometer.
Once it comes to temperature (I let mine come to 140º), transfer the mixture to a stand mixer fitted with a whisk attachment. Beat at speed 4-6 for until stiff peaks form, about five minutes depending on your mixer. Your meringue is now ready!
You can top your pie just before serving, but you can also top it and refreeze the pie until ready to use. There are two ways to put the meringue on your pie. First, you can just spread it on. Second, for a prettier look, place the meringue in a pastry bag fitted with a 1M tip. Pipe swirls all over the pie. There is just enough meringue to cover the top of the pie in one layer.
Use a kitchen blowtorch to lightly brown the tops of the meringue. Or, you can place the pie under the broiler for just a few seconds - do NOT walk away from the stove!
It’s easiest to slice frozen, but it tastes best after the slices sit at room temperature for a few minutes.