It has become somewhat of tradition at the Walsh family Christmas that I make some sort of cheesy potato dish. Layering a gratin can be as simple as mixing everything up and smashing it into a pan and baking it or you can take the time, and put the effort into making uniform layers with evenly distributed ingredients. This year I decided to put in that effort. Whether you decide to take the easy route or not, here is a list of ingredients that makes enough to fill a 10 inch square baking dish, and roughly 6-10 people.
Cheesy Potato Gratin
5-6 pounds large Idaho potatoes, cleaned and sliced 1/4 inch thick on a mandolin
1 onion sliced as thin as possible
8 oz cheddar
6 oz fontina
4 oz parmesan
1 pint heavy cream
5 egg yolks
1 heaping tablespoon roasted garlic
salt and pepper
Shred the cheeses and mix them together. Mix the cream, eggs, and roasted garlic together. Assemble the grain by nicely alternating layers of potato and cheese. Every third layer add some of the cream mix, but make sure you save some cream for the top and final layer. Don't forget to salt and pepper each layer.
Bake, covered at 400 degrees for about an hour and a half. Pressing the gratin at this point is optional. If you press it this makes unmolding it and cutting it into serving very easy. If you are serving it in the dish there is no reason to press it. To re-heat microwave until warm then bake for 5-10 minutes to form a crusty top.