We loved them too! I honestly think they are probably pretty close to a standard potatoes au gratin dish...the original au gratin would be made with lots of cream and some parmesan cheese...
Here's what I found on a UK Disney site:
Maui Scalloped Potatoes
from 'Ohana, Polynesian Resort
Yield: 1 ¼ lb.
1 lb. 70 count Idaho Russet potato (washed and sliced)
1 cup Heavy cream
¼ cup Cheddar cheese
2 TBSP Parmesan cheese
¼ cup Sweet onions
1 tsp Kosher salt
¼ tsp Black pepper
Combine all ingredients.
Place in a greased 2 hotel pan and bake at 350 ° Fahrenheit for one (1) hour.
Let stand for five (5) minutes before cutting.
Serve hot.