I couldn’t quite grasp the concept of a potato pie because to this point all I had been used to seeing was a sweet potato baked or sliced up and cooked.
Wash the potatoes and bake at 375 for 60 minutes. Add the ingredients, except for the water, into a food processor and pulse until it becomes like a meal.
Slowly drizzle in the water until the dough begins to slightly come together. Remove the dough and roll it out on a clean flour dusted surface so that it will fit into a 9” pie tin.
Form the dough to the pie tin and trim. Chill in the refrigerator until the sweet potatoes are done. Peel the sweet potatoes and add them to a large bowl along with all the other ingredients and mix.
While the pie is cooking add the egg whites, cream of tartar and sugar to a standing mixer with the whisk attachment and whisk on high speed until they’ve reached medium peaks, about 3 to 4 minutes.