Hi Renee :-) I found this information for you on the internet. The recipe I found is one that Judy/AZ posted here at recipelink. I think you could use any recipe for Au Gratin Potatoes (there are many already posted here at recipelink - just type the words "au gratin potatoes" in the search box) as long as you keep in mind that you will need 10 gallons to serve 200 people. I hope that this helps. Let us know. Good luck!

TABLE FOR 100 PLEASE
servings for 100 - divide to suit your needs

POTATOES (scalloped)
5 Gallons

(Scalloped potatoes are similar enough to au gratin potatoes that this amount should be the same.)

From: `Judy/AZ 10-19-2000
In reply to: ISO: Need recipe quickly!!!

I scaled this for 100 people for you. The recipe calls for an 8"x8" pan, no doubt you would have to use a large set of pans for this recipe for 100 people.

Au Gratin Potatoes

16 2/3 cups sour cream
16 1/2 (10.75 ounce) cans condensed cream of celery soup
74 cups peeled and shredded potatoes
33 cups shredded Cheddar cheese
8-1/3 cups chopped green onions
16 2/3 cups cornflakes cereal
8 1/3 cups unsalted butter, melted
1 cup and 1 tablespoon fresh chopped parsley (optional)

1. Preheat oven to 350 degrees F (175 degrees C). Spray one 8 inch square baking dish with vegetable cooking spray.

2. In a large bowl, combine sour cream and soup; mix thoroughly. Add grated potatoes, cheese and onions. Mix well; pour into baking dish.

3. Cover with foil and bake at 350 degrees F (175 degrees C) for 45 minutes.

4. In a small bowl, combine the corn flakes with melted butter; sprinkle over potatoes.

5. Bake uncovered, for an additional 20 minutes or until bubbly and corn flakes are golden brown. Remove from oven and sprinkle with chopped parsley if desired.

This recipe has been scaled to yield 100 servings.
Original recipe makes 6 servings.