Zucchini & Summer Squash Gratin with Parmesan & Fresh Thyme

Zucchini & Summer Squash Gratin with Parmesan & Fresh Thyme

Ingredients

For the onions:

  • 1 Tbs. olive oil
  • 1 medium onions, thinly sliced
  • 1 clove garlic, minced

To assemble the gratin:

  • 3/4 lb. ripe tomatoes, cored and cut into 1/4-inch slices
  • 1 zucchini, cut into 1/4-inch slices on the bias
  • 1 yellow summer squash, cut into 1/4-inch slices on the bias
  • 1 1/2 Tbs. olive oil
  • a handful of fresh thyme leaves
  • 1/2 tsp. coarse salt
  • 3/4 cups freshly grated parmigiano reggiano
  • Freshly ground black pepper to taste

Preparation

  • To cook the onions: In a medium skillet, heat the olive oil over medium heat. Add the onions and sauté, stirring frequently, until limp and golden brown, about 20 minutes. Reduce the heat to medium-low if they’re browning too quickly. Add the garlic and sauté until soft and fragrant, 1 to 2 minutes Spread the onions and garlic evenly in the bottom of an oiled dish. Let cool.
  • To assemble the gratin: Heat the oven to 375°F. Put the tomato slices on a shallow plate to drain for a few minutes and then discard the collected juices. In a medium bowl, toss the zucchini and squash slices with 3/4 Tbs. of the olive oil, 1/2 Tbs. of the thyme, and 1/4 tsp. of the salt. Reserve half of the cheese for the top of the gratin. Sprinkle 1/2 Tbs. of the thyme over the onions in the gratin. Starting at one end of the baking dish, lay a row of slightly overlapping tomato slices across the width of the dish and sprinkle with a little of the cheese. Next, lay a row of zucchini, overlapping the tomatoes by two-thirds, and sprinkle with cheese. Repeat with a row of squash, and then repeat rows, sprinkling each with cheese, until the gratin is full.
  • Season lightly with pepper and the remaining 1/4 tsp. salt. Drizzle the remaining 3/4 Tbs. olive oil over all. Combine the reserved cheese with the remaining thyme and sprinkle this over the whole gratin. Cook until well-browned all over and the juices have bubbled for a while and reduced considerably, 65 to 70 minutes. Let cool for at least 15 min. before serving.