Gratin, scalloped or lyonnaise - the allure of a potato casserole

It is cold, very cold, outside.  My body is begging for warm, stick to your ribs, comfort food.  

When it comes to side dishes involving potatoes I've been in a definite rut - mashed or oven roasted.  I really want a potato dish combining the best attributes of both preparations, the "bite" of oven roasted with the creaminess of mashed.  I had vague memories of my mom's "scalloped" potatoes.  A casserole of sliced potatoes and  Campbell's Cream of Mushroom soup.  A start, but I knew better options were out there.  

So, what is the difference between a gratin, lyonnaise and scalloped potatoes?  A gratin has a lightly browned crust of cheese.  Lyonnaise must have onions and usually white wine, no cheese required.  Scalloped potatoes, are a little harder to define.  I think it is any creamy casserole of sliced potatoes:  cheese and onions are optional.

So after a little research I produced the following potato gratin to rave reviews.  Most of the recipes I found were heavy handed with fat, using a cup of heavy cream, a cup of grated Gruyere cheese, and generous dabs of butter on the top.   As delicious as that sounded I wanted something a little heart healthier so settled on 1/2 cup of half 'n half combined with 1/2 cup of water, and omitted the butter on the top.  My cheese was limited to what I had on hand, that day only three slices of Swiss and some grated Parmesan.  Next time I'll experiment with blue cheese or chevre, two staples of my refrigerator

Gratin of Potatoes - serves 4 to 6 as a side dish

4 to 5  medium size Yukon Gold Potatoes

1/2 cup half 'n half

1/2 cup water

1/4 c. grated Parmesan

1/2 c. grated Gruyere or Swiss cheese

1 medium shallot, finely minced

butter

salt

pepper

Preheat oven to 425 degrees.

Butter the sides and bottom of a 1.5 to 2 quart casserole. I used a 8" by 8" Pyrex dish.

Peel potatoes and cut into 1/8"  slices.  

Layer the potatoes in the baking dish, sprinkling shallot, and cheeses between each layer.  The final dish should be 3 or 4 layers thick.

Combine water and half and half.  Add dashes of salt & pepper. Mix and pour over potatoes.

Cover the dish with aluminum foil and bake for 25 minutes.  Uncover, sprinkle generously with remaining Parmesan cheese and bake an additional 20 minutes, or until there is a light brown crust and the potatoes  are tender to the fork.