I've yet to meet a gratin I didn't want to marry. Comfortable unpretentiousness, warm and welcoming, and so flexible. It can be a stand-alone dish, needing only a salad to round it out, or be one of many side dishes on a Thanksgiving table. It can be healthy or not-so-much, and accommodate almost any vegetable or fish. Cooking something au gratin means to bake it with a crust made of shavings of cheese and/or breadcrumbs. The word stems from a French word (yes, this dish is from the ...