Just in time for the holidays, Cousin Matthew and I will offer you two versions of Potatoes au Gratin, today and Thursday. As Cousin M says, everyone makes them differently. Making them from scratch, as opposed to opening a box and re-hydrating cardboard potatoes mixed with powdered cheese is well worth the effort. My recipe combines a version from Martha Stewart and a version from my Grandmother’s favorite cookbook, Meta Given’s 1949 classic The Modern Encyclopedia of Cooking.
Preheat your oven to 300-325 F and butter a 2 quart baking dish, set aside. Thinly slice (1/8 inch or so) two-three pounds of potatoes (whatever you have on hand works, err to the side of larger), set aside.
Now, start the sauce. Heat 1 and 1/2 to 2 cups of heavy cream (depending on how many potatoes you use), 1 tsp salt, 1/4 tsp black pepper, 2 pinches of saffron, and 1/4 tsp grated nutmeg. Bring to a simmer, so that the sauce is boiling at the edge of the sauce pan but not at a full boil. Remove from the heat and set aside – you want it to cool and thicken a bit.
While your sauce cools, slice 1 very large onion (I like Vidalia) and uncoil into rings. Add 1-2 Tbls butter to a frying pan and heat to a light sizzle, then add the onion and 1 Tbls minced garlic. Salt and cook until translucent, maybe 10 minutes, stirring as needed. Lower the heat and continue to cook until the onion is caramelized, a golden brown color throughout, about 15 minutes. Watch them – you do not want to burn them.
Layer half the sliced potatoes in the buttered dish, overlapping them into a scale or shingle pattern. Layer on the onions and 1/2 cup grated Gruyère cheese. There is really no substitute for this type of cheese – you may need to go to a fancy grocery to get some. Layer the rest of the potatoes and pour the cooled sauce over all; finish with another 1/2 cup grated Gruyère cheese.
Bake for 1 hour and 30 minutes; pull out of the oven and let stand for 15 or 20 minutes to allow the sauce to further set. These can be made ahead, covered with foil, and popped in to reheat with other dishes.