Ratatouille Gratin

A mandoline makes quick work of slicing the vegetables for this simple yet sophisticated play on ratatouille, a Nicoise vegetable dish that is traditionally made with tomatoes, eggplant and squash.


  • 4 Tbs. olive oil
  • 2 tsp. chopped garlic
  • 2 tsp. chopped fresh thyme
  • 1 yellow onion, thinly sliced
  • Salt and freshly ground pepper, to taste
  • 4 large roma tomatoes, sliced into 1/8-inch (3-mm) rounds
  • 2 large zucchini, sliced into 1/8-inch (3-mm) rounds
  • 2 large summer squashes, sliced into 1/8-inch (3-mm) rounds
  • 1 Japanese eggplant, sliced into 1/8-inch (3-mm) rounds


Preheat an oven to 400F (200C).

In a 12-inch (30-cm) stainless-steel gratin over medium heat, warm 1 Tbs. of the oil. Add the garlic and thyme and cook, stirring occasionally, until fragrant, about 1 minute. Transfer to a large bowl and set aside.

Add another 1 Tbs. of the oil to the gratin and return to medium heat. Add the onion and cook, stirring occasionally, until the onions are tender and lightly caramelized, 12 to 15 minutes. Remove from the heat, season to taste with salt and pepper, and spread the onions to cover the bottom of the gratin.

Arrange the tomato slices in a single layer on paper towellined plates to absorb any excess liquid. Season with salt and pepper. Set aside.

Add the zucchini, squash and eggplant slices along with remaining 2 Tbs. olive oil to the bowl with the garlic-thyme mixture. Toss until well combined and season with salt and pepper.

To build the gratin, arrange overlapping slices of squash, eggplant and tomato, as if they were shingles, around the edge of the gratin. Continue by making a second ring of overlapping vegetable slices inside the first and finish with a row of overlapping slices down the center of the gratin.

Bake until the vegetables are lightly browned and tender, about 45 minutes. Let rest 5 minutes before serving. Serves 6.

Williams-Sonoma Test Kitchen

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