Cut and pit the plums and put them in a bowl. Add the sugar, flour, tapioca, lemon, salt and nutmeg. Stir until coated.

Roll out the bottom crust and ease it into the pie plate. Spoon the filling into the crust and top it with the second crust. Trim, roll and crimp the edges to finish.

Put the pie in the freezer. Preheat the oven to 425. Give it at least 20-25 minutes to make sure it's fully preheated.

Lightly beat the white of one egg.

When the oven is preheated, take the pie out of the freezer. Cut a few decorative (but also functional) vents in the top crust. Brush the top crust and the edges lightly with the egg white and sprinkle sugar over the top.

Place the pie on a parchment-lined, lipped baking sheet, and bake it at 425 for 20 minutes. Then reduce the heat to 375 and bake for 45-55 minutes more, until you can see juices bubbling thickly through the vents and the pastry is a deep, golden brown.

Remove the pie from the oven and let cool on rack. The filling will hold together best if you give it 6 to 8 hours to cool.