Friday Finds: Summer Vegetable Gratin

This is the final post in my (very drawn out) series of post-Easter dinner posts.  It's the second Friday Finds in a row that I am featuring a recipe from chef Thomas Keller's Ad Hoc at Home cookbook.  Chef Keller didn't let me down this time either.  That roasted onion recipe was delicious and this summer vegetable gratin is a simple yet impressive side dish. I know it's a little premature to make a "summer" vegetable dish in April (especially since we saw snowflakes this past weekend-- yikes!), but I'm sure it would be even better in the summer with fresh summer vegetables.  I will definitely keep this recipe in mind when we're shopping at Green City Market this summer.

Ingredients:

• 2-3 Roma tomatoes
• 1 medium yellow squash
• 1 medium zucchini
• 1 small eggplant
• Canola oil
• 2 1/2 cups onions, coarsely chopped
• 2 garlic cloves, finely minced
• Kosher salt
• 1 Tbsp., plus 1 tsp. fresh thyme, chopped
• 1/4 cup extra virgin olive oil, plus more for drizzling
• Freshly ground black pepper
• 1/2 cup Parmesan, grated
• 1/2 cup bread crumbs

Preheat oven to 350 degrees. Set a cooling rack on a baking sheet. 

Slice the vegetables to end up with slices as close in size as possible. Slice the tomatoes into 1/4-inch slices (discard the end slices). Trim the yellow squash, zucchini, and eggplant and cut into 1/4-inch-thick slices: if necessary, cut them on a slight diagonal so the slices are about the same size as the tomato slices.

Heat some canola oil in a large frying pan over medium heat.  Reduce the heat to medium-low, add onions and garlic, season with salt.  Cook without browning, stirring occasionally, until the onions are translucent, about 20 minutes.  Stir in 1 Tbs. thyme.

Combine the yellow squash, zucchini and eggplant in a large bowl and toss with 1/4 cup olive oil, and season with salt.  

Drizzle the tomato slices with olive oil and season with salt.

Combine the parmesan, breadcrumbs, and remaining 1 tsp. thyme in a small bowl.

Spread the  onion mixture in the bottom of a 13.5x9.5 baking dish (or 13-inch round baking dish).  Layer the vegetables in the dish, working on the diagonal.  Arrange a layer of overlapping slices of one-third of the zucchini around the outside edge of the dish. Sprinkle 2-3 Tbs. of the cheese mixture over the top. Make a row of overlapping slices of yellow squash slightly overlapping the zucchini, and sprinkle 2-3 Tbs. of the cheese mixture over the top. Make a third row with overlapping slices of tomatoes, slightly overlapping the zucchini, and sprinkle with the cheese mixture. Make a fourth row with overlapping slices of eggplant, slightly overlapping the tomatoes, and sprinkle the cheese mixture over the top. Continue making overlapping rows of the remaining vegetables, and sprinkle the top with any remaining cheese mixture and a light sprinkle of salt.

Bake for 1 to 1 1/2 hours until the vegetables are completely tender and offer no resistance when pierced with a knife.  Remove from oven and allow the gratin to rest for 10 minutes.  Turn on the broiler and place the gratin under the broiler to brown the top just before serving.