Use white potatoes. Adjust portions to suit your needs. I usually plan on at least 1 or 2 medium sized potatoes per serving.
Peel and slice potatoes.
Butter bottom of pan. Put a layer of sliced potatoes in pan.
Sprinkle Wondra flour over top and salt/pepper to taste.
Dot top with butter.
Add layers until ingredients are gone (usually 2 or 3 layers).
Add enough milk to cover about 1/2 of the potatoes layers (enough to just see it in pan).
Bake at 350 for 1 hour. If you like the top brown you can broil for a couple minutes at the end.