Place ingredients in the order listed (minus potato starch, plums and sprinkling sugar) into your bread machine and select the dough program. To make the traditional dough recipe, follow the video instructions.
Preheat oven to 325°F/160°C.
When the dough is ready, roll out the dough on a lightly floured surface, into the shape of the baking tray. Roll it out to about ½ cm thick, or ¼ inch thick and place on top of the parchment.
Lightly sprinkle the dough with potato starch before your place the plums. Best to use a sieve for even spreading. This will help soak up the juices as it cooks, and the dough won't seem unbaked.
Split the plums in half, remove the seed, and place the plums side by side covering the dough (split side facing up). The dough should be covered as much as possible with the plums.
Place in the the oven for about 20 minutes until the dough starts to turn golden brown. To keep the sides of the dough from burning, cover with foil and return to over for another 20 minutes. Check that the base of the pie is cooked underneath and that the fruit is soft and juices start to release. If needed, keep in oven and keep checking until you are happy with it. Mine took around 50 minutes.
Remove from the oven and generously sprinkle sugar on top of the plum pie. Serve with whipping cream or ice cream.