Summer Squash and Herb Gratin

The most obvious solution to the “problem” of those oversized, seed-filled summer squash is to make a gratin. When you slice those massive squash as thinly as possible, blanket them in something creamy, and top the pile with something crunchy, the so-called problem is a problem no more.

However, gratins cause a problem of their own (one that’s slightly more real than a glut of summer produce): flooding. Summer squash are like 80% water, and if you aren’t careful, they’ll flood even your most carefully constructed casserole. If you’ve ever made a gratin with plain sliced squash, you know what I’m talking about. You’ve gotta serve it with a slotted spoon, and even then, the liquid pools in the pan and on the plate, ruining what could have been a good thing.

Most recipes that call for cooked squash tell you to salt and strain it in advance. This is good advice. But to really avoid any pooling whatsoever, you need to kick the draining process into overdrive.

Before making this gratin, I salted my squash aggressively and let it strain for a full hour. I then pressed it against the strainer to release even more liquid, and before layering it into the gratin dish, I picked up handfuls and squeezed them out even more. For about 2 1/2 pounds of squash, I ended up with 1 1/2 cups of liquid. That’s 1 1/2 cups of liquid that didn’t flood my gratin dish. Winning.

A side benefit of straining the squash so aggressively is that the process softens it, so it takes much shorter to cook. As a result, the gratin didn’t taste like it had been cooked to death. It was soft and yielding, but still tasted fresh.

I kept the flavoring pretty simple – just a big handful of my favorite herbs from the garden: basil, mint, chives. If you’ve got some pesto in your fridge, you can use that instead.

Also, as good as an uber-creamy gratin can be, I wanted to keep this one light, for summer. That didn’t stop me from making a bechamel, but I just made a half portion of it, and spread it on top of the casserole before topping with the breadcrumbs. The result was light enough to fall short of indulgent, but that layer of bechamel stays creamy underneath and gets crunchy on top: it makes the gratin, so don’t skip it.

Summer Squash and Herb Gratin
Serves 4 with leftovers, or 6 if served as a side dish

2 1/2 lbs. summer squash
1 tablespoon salt
3 tablespoons olive oil, divided
1 cup fresh bread crumbs
1 medium-large yellow onion, diced
1/4 cup chopped fresh herbs (I like a mixture of basil, mint, and chives, but you can use oregano, parsley, or whatever herbs you have) 3 tablespoons butter
2 tablespoons flour
1 cup milk
1/2 teaspoon nutmeg, preferably fresh
1/2 cup grated parmesan cheese
Salt and pepper

Using a mandoline, slice the squash into 1/6-inch slices. Layer them into a large strainer, sprinkling the tablespoon of salt over the slices layer by layer until all the squash has been salted and layered into the strainer. Put the strainer over a bowl or in the sink, and set aside to drain for one hour. Once an hour has passed, press hard on the squash to release as much liquid as possible.

Preheat the oven to 375 degrees and lightly butter the inside of a roughly 9×13″ baking dish.

Put 1 1/2 tablespoons of the olive oil into a saute pan set over medium heat. Add bread crumbs, and cook, stirring occasionally, until golden browned and crispy, 5-7 minutes. Strain into a small bowl.

In the same pan, add the remaining 1 1/2 tablespoons olive oil and the diced onion. Cook over medium heat, stirring occasionally, until translucent, about 5 minutes. Transfer onions to the bottom of the baking dish.

Now, make the bechamel: in a small saucepan, melt butter until it bubbles. Add flour, and use a fork to stir until it has combined with the butter to form a creamy paste. Add the milk and a pinch of salt, turn the heat to medium-high, and bring the milk to a boil. Boil for about 1 minute, stirring regularly, until the sauce thickens. Then stir in the nutmeg and remove from the heat.

Assemble the gratin: Take handfuls of the strained squash, give them a strong squeeze to release their liquid, and layer or pile them into the baking dish, adding bits of chopped herbs as you go. You don’t have to be fancy with the layers here: the whole thing gets covered up anyway. When you’ve layered in half the squash and herbs, sprinkle a couple tablespoons of the bread crumbs and one or two gratings of cheese over that layer. Shake a few grinds of pepper over that layer as well. Repeat with the remaining squash and herbs, top with a thin layer of cheese, then spoon and spread the bechamel over the top. Sprinkle the breadcrumbs and the remaining cheese onto the bechamel.

Transfer to the oven and bake for 30 minutes. Serve immediately, or let cool completely and store for up to 3 days. Reheat gratin in a 375-degree oven for at least 15 minutes before serving.