T.G.I. Friday's Au Gratin Potatoes

4 Large baking potatoes
3 Cups Bechamel sauce (see following recipe)
1 teaspoon salt
1/4 teaspoon white pepper
3/4 cup grated Mozzarella cheese
1/4 cup grated Colby cheese
Bake potatoes in oven at 400 degrees until completely
cooked. Cool for 30 minutes at room temperature, then slice
into 1/2" thick rounds. Mix together the Bechamel sauce, salt
and white pepper. Add remaining ingredients.
Fold in potatoes. Place mixture in covered baking dish in a
300F oven for 1 hour, or until potatoes are hot all the way
through. Remove the cover and allow potatoes to brown.
Bechamel Sauce
1 quart half & half
2 ounces flour
2 ounces clarified butter
salt and pepper to taste
In a saucepan, combine the flour and butter. Cook over a
low flame, for about 15 minutes until the mixture begins
to bubble. Stir frequently so the roux does not color.
Gradually add the half & half, stirring out the lumps as
it thickens. After the entire amount of half & half has
been added, cook for 45 minutes over a low flame, stirring
occasionally to keep the mixture from sticking to the saucepan.
Season to taste with salt and pepper.