Summer Squash Gratin with Salsa Verde & Gruyère



Most of the time when I think of a vegetable gratin, I think of thinly sliced potatoes and root vegetables baked with cream in a wide, shallow dish until meltingly tender and browned on top. (If you aren't familiar with this type of gratin, I posted a recipe for one last November.) But of course this isn't the only type of vegetable gratin. Any vegetable (or combination of vegetables)—sliced or not—baked in a shallow dish and browned on top (gratinéed) is a vegetable gratin. A few years ago I ran across an unusual recipe for a Summer Squash Gratin in Suzanne Goin's Sunday Suppers at Lucques. Whereas the more well-known gratins are made rich with cream and are more appropriate for winter dining, this one featured olive oil and lots of fresh herbs—making it a perfect addition to the summer table.

One of the reasons I like this gratin is that when it comes out of the oven the squash is just tender—not soft and mushy. Goin employs a couple of techniques to insure this result. The first is to salt the squash slices to draw out as much excess liquid as possible before assembling the gratin.

Summer squash is loaded with water. If some of this water isn't removed before baking, it would be released during the cooking process. The squash would boil in its own liquid and the resulting gratin would be unappetizingly soggy.

To further guard against producing a wet and sloppy gratin, Goin puts breadcrumbs in the gratin—not just on top of it. These additional breadcrumbs absorb any liquid not removed by the salting process. The breadcrumbs are also a great source of additional flavor. Before adding them, they are tossed with browned butter (see my post on Butter Pecan Ice Cream for more information on browned butter). The nuttiness of the browned butter emphasizes the mildly nutty character of the summer squash.

To make the fresh breadcrumbs, use a "day old" loaf of a nice artisanal style bread. A country French boule, a good baguette or a substantial ciabatta would all be fine. If I happen to have it on hand, I've found that a local bakery's Rosemary and Olive Oil bread is a particularly good choice. If the crusts of your loaf are unusually hard, cut them off and just use the interior of the loaf. Tear the bread into chunks and put it in the food processor and process until you have coarse crumbs.

The main thing that attracted me to this gratin in the first place was its use of salsa verde. Salsa verde is one of my favorite sauces—especially for summer foods. (Regular readers may remember that I wrote about it earlier this month.) But when I use salsa verde, I almost always use it as a finishing touch—drizzled over vegetables or fish, for example. This recipe used it as a component...adding it to the gratin before it was baked. As the gratin bakes, the squash is infused with the vibrant flavors of the sauce.

This recipe is typical of the kinds of recipes used in restaurant kitchens in that it uses another completed recipe as an ingredient.  In a restaurant setting, this is a huge time saver.  But for the home cook, it probably seems like a lot of work to make the Salsa Verde just to add it to the gratin. You could of course simply incorporate all of the ingredients that are in the salsa verde directly into the gratin and forgo making the sauce separately. But if you do go to the trouble of making the sauce, you will have a nice drizzle for whatever meat you are serving with the gratin—which is what Goin suggests in her book. Another work-saving option would be to plan for two meals and make a large batch of salsa verde. Serve it the first night as a sauce and then use it the next night in the gratin.

The important thing is to avoid making the mistake of bypassing this recipe because it looks complicated. If broken down into steps (sliced squash, browned butter-breadcrumbs, salsa verde, grated cheese, seasonings)—all of which can be done ahead—the final dish can be assembled and baked quickly. And it is so worth making...even if you think you don't like summer squash. This could be the dish that changes your mind.

Summer Squash Gratin with Salsa Verde & Gruyère

1 1/2 c. fresh breadcrumbs (see note)
3 T. unsalted butter
2 lbs. summer squash
3/4 c. thinly sliced shallots
1 t. minced garlic (1 large or 2 small cloves)
1 T. fresh thyme leaves
1/2 c. salsa verde
4 oz. grated Gruyère (about 1 cup)
Salt & Pepper

Place the breadcrumbs in a bowl. In a small sauté pan cook the butter over medium heat for a few minutes, swirling occasionally, until it begins to brown and smells nutty.   Pour the butter over the breadcrumbs, scraping in all of the browned bits. When cool enough to handle, toss to combine. Set aside.

Using a mandoline-type slicer, cut the squash into 1/8-inch thick slices, slicing on a long diagonal if you are using Zucchini-type summer squashes. Toss the squash slices with 1 t. kosher salt and place in a colander set over a plate. Let stand 10 minutes.

Transfer the squash to a large bowl, shaking off as much of the liquid as possible. (If you are so inclined, spread the squash in a rough layer on a double thickness of paper towels and blot dry—this is a bit more effective than shaking the liquid off—then transfer to the bowl.)

Add the remaining ingredients and half of the breadcrumbs and season to taste with salt and pepper. Toss until the ingredients are well combined and evenly distributed. Taste and correct the seasoning.

Transfer the squash to a shallow 2-quart gratin (roughly 9- by 9-inches). Scatter the remaining breadcrumbs over the top and bake in a preheated 400° oven until the squash is tender and the top is golden and crisp—about 35 to 40 minutes. Serve hot or at room temperature. Serves 8.

(Recipe adapted from Sunday Suppers at Lucques, by Suzanne Goin)