Boil potatoes until they fall to pieces.

Let cool then remove skins.

Mash potatoes in the water to make a puree. (you need at least 2 cups)

Pour into a large pot. (I use an old clay 4qt. bean pot).

Mix in flour and sugar, and let sit covered in a warm place for at least 3 days stirring once or twice each day. Add water if too thick.

After the 3rd day it should be bubbling nicely and ready to use.

Surprise:.

I kept my starter going for 10 yrs. and 2 moves. I just kept adding 1 C flour and 1-2 teaspoons sugar at a time to build it up, and used it a day or two later.