From Linda McCartney´s Home Cooking, p. 117
Linda recommends serving this piping hot- which tastes great. I tried taking leftovers to work with me and it was also good as a cold lunch. The Potato Torte was not quite set when it came out of the oven but was perfect when cooled.
The recipe starts with pre-heating the oven, which is too early as you have to cook the potatoes for at least 20 minutes. Start pre-heating as soon as the potatoes are soft.
I needed to bake my potato shell for 20-25 minutes as it was still very soft after 15 minutes.
Gluten-free: Use gluten-free flour (e.g. from Doves Farm)
Vegan: Substitute the mozzarella and parmesan for vegan cheese.