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Summer Squash, Leek, Spinach & Parmesan Gratin

Servings: 6 to 8

Over the years, I’ve done many Provençal “tians” or gratins of layered summer vegetables, and they’re always a crowd favorite. I love this version: zucchini and summer squash, layered with Parmigiano on a bed of silky leeks and baby spinach.


  • 2 Tbs. unsalted butter; more for the baking dish
  • 1-1/2 cups coarse fresh breadcrumbs (from about 2 English muffins)
  • 1-1/2 cups coarsely grated Parmigiano-Reggiano or Grana Padano (about 7 oz.)
  • 1/2 cup extra-virgin olive oil; more as needed
  • 2-1/2 Tbs. coarsely chopped fresh thyme leaves
  • Kosher salt
  • 4 large leeks, white and lightgreen parts halved lengthwise and cut crosswise into 1/4-inch-thick slices (about 4 cups)
  • 2 tsp. minced garlic
  • 6 oz. baby spinach (about 6 packed cups)
  • 2 lb. summer squash (a mix of varieties and colors), cut crosswise on the bias into 1/4-inch-thick slices (about 4 medium squash)
  • Freshly ground black pepper

Nutritional Information

  • Calories (kcal) : 290
  • Fat Calories (kcal): 200
  • Fat (g): 23
  • Saturated Fat (g): 7
  • Polyunsaturated Fat (g): 2.5
  • Monounsaturated Fat (g): 12
  • Cholesterol (mg): 25
  • Sodium (mg): 790
  • Carbohydrates (g): 16
  • Fiber (g): 2
  • Sugar (g): 2
  • Protein (g): 7


  • Place a rack in the center of the oven, and heat the oven to 350°F. Rub a 4-quart shallow gratin or other shallow baking dish (a 15x10x2-inch Pyrex dish is fine) with a little butter.
  • In a medium bowl, combine the breadcrumbs, 1/4 cup of the Parmigiano, 2 Tbs. of the oil, 2 tsp. of the thyme, and 1/2 tsp. salt. Stir well to combine, and set aside.
  • In a large, heavy-duty nonstick skillet, melt the 2 Tbs. butter with 2 Tbs. of the oil over medium-low heat. Add the leeks (it’s okay if some water clings to them) and 1/2 tsp. salt. Cover and cook, stirring occasionally, until the leeks are softened and translucent, about 5 minutes. Uncover, raise the heat to medium, and continue to cook, stirring frequently, until the leeks are shrunken and browned in places, about 6 minutes more. Add 2 tsp. thyme and the garlic, and stir until fragrant, about 30 seconds. Carefully add all of the spinach to the pan, and toss with the leeks until the spinach is wilted, about 1 minute. Transfer the leeks and spinach to the gratin dish, and use a spatula to smooth into an even layer.
  • Put the sliced squash, the remaining 4 Tbs. olive oil, the remaining 3-1/2 tsp. thyme, and 2 tsp. salt in a mixing bowl. Add several grinds of pepper, and stir until the squash is thoroughly coated.
  • Beginning at one end of the gratin dish, arrange a row of slightly overlapping squash slices, slightly propped up against the edge of the pan. Sprinkle with Parmigiano, using about 1-1/2 Tbs. per row. Shingle another row of squash slightly overlapping the first, sprinkle with Parmigiano, and continue arranging until the pan is full. If you think you’re going to come up short, push down on the rows with the palm of your hand to spread them out somewhat. (If you think you are going to have a lot of extra squash, you can push the rows back to make room for more. You’ll usually wind up with a few extra pieces.)
  • Drizzle whatever liquid is left in the mixing bowl over the vegetables, and sprinkle them with any remaining Parmigiano. Drizzle with a bit of olive oil. Cover the top with the breadcrumb mixture. Bake until the squash is tender and the top of the gratin is deep golden ( juices will bubble and darken around the edges), about 45 minutes, rotating the pan halfway through baking for even browning. Let sit at least 15 minutes before serving.


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Reviews (7 reviews)

  • user-41257 | 07/07/2019

    Outstanding recipe. Definitely a case where the whole is greater than the sum of its parts. Only thing to point out: definitely only "lightly butter" the dish, otherwise there will be pools of butter in the final product.

  • conhall | 09/24/2018

    This has been my "Summer 2018 Best Of" Recipe winner. I think I've made this at least five times. And every time, people ask for the recipe. Phenomenal.

  • tlamo | 09/03/2018

    This is just extraordinary. We have loads of leeks in the garden, and this was a great way to use them. It’s a bit labour intensive, but the result is more than worth it. The only change I made was to use young leaves of swiss chard instead of spinach, as this is we had in our garden. Absolutely delicious.

  • tscorpa | 08/14/2018

    Made this without the leeks since my wife does not like them. We really enjoyed it. The English muffin breadcrumbs was brilliant, made nice chunky bread crumbs that crisped up well.

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