Zucchini & Summer Squash Gratin with Parmesan & Fresh Thyme

This summer has been all about squash for me. This weekend, my neighbors gave me some squash from their friend's garden that looks like it's on steriods. They are HUGE. I started brainstorming a good way to use it all up and decided on doing a gratin. I poked around on the internet and found this recipe on FineCooking.com and look forward to making it tonight. I don't have any thyme in my kitchen but I have basil so I am going to use that instead. For some crunch, I am going to mix a little panko and olive oil and spread a thin layer on top before baking.

Zucchini & Summer Squash Gratin with Parmesan & Fresh Thyme

For the onions:
2 Tbs. olive oil
2 medium onions (14 oz. total), thinly sliced
2 cloves garlic, minced

To assemble the gratin:
1-1/4 lb. ripe red tomatoes, cored and cut into 1/4-inch slices
3/4 lb. (about 2 small) zucchini or other green summer squash, cut into 1/4-inch slices on the bias
3/4 lb. (about 2 small) yellow summer squash or golden zucchini, cut into 1/4-inch slices on the bias
3 Tbs. olive oil
1/4 cup fresh thyme leaves
1 tsp. coarse salt
1-1/4 cups freshly grated parmigiano reggiano
Freshly ground black pepper to taste

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 2-qt. shallow gratin dish (preferably oval). 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 1-1/2 Tbs. of the olive oil, 2 Tbs. of the thyme, and 1/2 tsp. of the salt. Reserve half of the cheese for the top of the gratin. Sprinkle 1 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 1/2 tsp. salt. Drizzle the remaining 1-1/2 Tbs. olive oil over all. Combine the reserved cheese with the remaining 1 Tbs. 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.

Zucchini & Summer Squash Gratin with Parmesan & Fresh Thyme