This is an update of a recipe I did for Fine Cooking magazine many years ago. It was part of a story I did on tians, which are Provençal vegetable gratins. There’s no cream in a tian — just rows of thinly sliced vegetables (always some tomato), often over a base of aromatics (in this case, sautéed leeks). And cheese and herbs, of course! I’ve done them with summer squash and with eggplant, but this one, with potatoes, Gruyère and leeks, is perfect for early fall on the Vineyard. The trick is not to undercook the tian — the flavor comes from letting the tomato juices reduce down and combine with the earthy-sweet flavor of the leeks. Be sure to use freshly made coarse breadcrumbs. A seeded or multi-grain loaf is a nice match.
You will want a (2-quart) shallow gratin dish for this tian. An oval ceramic or enameled cast-iron dish is ideal, but a Pyrex baking dish will do. Just don’t choose a steep-sided casserole.
Serves 6 to 8 as a side dish
For the leeks:
- 1 ½ tablespoons olive oil
- 3 ½ cups thinly sliced leeks (about 3 large, white and light green parts only), submerged in a bowl of tepid water to release dirt
For the potatoes:
- 1 pound red potatoes, unpeeled, cut into ¼-inch slices
- Kosher salt
- 2 teaspoons chopped fresh rosemary
- 1 ½ tablespoons olive oil
To assemble the gratin:
- 1 teaspoon chopped fresh rosemary
- 1 1/2 pounds ripe tomatoes, cored and cut into ¼-inch slices
- 2 (generous) cups grated Gruyère cheese
- Kosher salt
- 1 ½ tablespoons olive oil, plus 1 teaspoon for the breadcrumbs
- 1 cup coarse fresh breadcrumbs
Cook the leeks:
1. Heat the olive oil in a medium skillet (preferably nonstick) over medium heat. Lift the leeks out of the bowl of water with your hands and transfer them (still dripping with water) to the skillet. Cook, stirring frequently, until the water cooks out, the leeks are limp and shrunken, and the leeks begin to turn golden brown in many places, about 15 minutes. Spread the leeks evenly in an oiled 2-quart shallow gratin dish. Let cool.
Cook the potatoes:
1. In a medium saucepan, cover the potato slices with well-salted water and bring to a boil. Reduce the heat to a simmer and cook for 5 minutes, or until the slices are just barely tender. Drain and rinse gently with cold water. Drain well and spread on a large sheet pan to continue cooling for a few minutes. Season the potatoes with ½ teaspoon salt and the 2 teaspoons chopped rosemary. Drizzle with the 1½ tablespoons olive oil and gently toss until the potatoes are lightly coated with oil and seasonings.
Assemble the gratin:
1. Heat the oven to 375°F. Sprinkle ½ teaspoon of the chopped rosemary over the leeks.
2. Starting at one end of the baking dish, lay a row of slightly overlapping tomato slices across the width of the dish. Prop the tomatoes against the end of the dish at a 60° angle. Cover the row of tomatoes with a nice sprinkling of Gruyère.
3. Next, arrange a row of overlapping potato slices over the tomatoes so that they are leaning up against them and covering all but a little bit of the tomatoes at the top. Sprinkle again with Gruyère. Repeat with alternating rows of tomatoes and potatoes, sprinkling each with cheese, until the gratin is full. You will probably have more or less of the tomatoes or the potatoes; don’t worry – it never works out perfectly. But as you go along, if you think you are going to have a lot extra, you can gently push the rows back towards the end of the dish you started at, scrunching them up a bit to open more space.
4. Sprinkle about ½ teaspoon salt and the remaining rosemary over all. Drizzle with the 1½ tablespoons olive oil.
5. Mix the breadcrumbs with a pinch of salt, a teaspoon or two of olive oil, and any remaining cheese (if there is any). Sprinkle evenly over the vegetables.
6. Cook until the tian is well-browned all over and the juices have bubbled for a while and reduced considerably, 60 to 65 minutes. Let cool for at least 15 minutes before serving. The tian is delicious reheated the next day, too.
