Zucchini Is a Terrible Pizza Topping! (Unless You Treat It Right)

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[Photographs: J. Kenji López-Alt]

I love good summer zucchini, but let's face it: It's not the most exciting vegetable in the world. In fact, it's one of the blandest. That's why, whether I'm sautéeing it or grilling it, I always try to hit it with as much heat as possible. There's just no other way to give it a nice, browned flavor before it has a chance to over-soften and turn into mush.

It's for this reason that zucchini makes a terrible pizza topping.

But wait a minute! I can hear you say. Doesn't a pizza oven get really, really hot, which is exactly what you want for zucchini?

Well, yes, it does, but the problem is that pizza ovens cook primarily by convection of hot air, and air is not a particularly efficient means of heat transfer. Even in a 900°F pizza oven, you won't get any browning at all on a slice of zucchini by the time the pizza crust has finished cooking. Every zucchini-topped pizza I've had in the past has been a watery disappointment. If there's one thing I love, it's being not-disappointed. So I made it my goal to come up with a technique for topping pizza with zucchini that really works.

Wet Zucchini Contest

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My first thought was to try slicing the zucchini in different ways, ranging from chunks (watery and mushy), to matchsticks (watery and soft), to thin, thin slices that I made on a mandoline (watery and bland). No matter what I did, I couldn't get around the fact that zucchini simply has too much water in it to work.

What I needed was to get rid of that excess moisture before adding it to the pizza.

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Use the force, Kenji, I heard a voice say out of nowhere.

But which force? Gravitational? Van der Waals? Nuclear?

No, silly. The force produced when the Brownian motion of a solute moves it toward a permeable membrane, which it is then repelled from by electrostatic forces that result in a pressure change that pushes water across that membrane from an area of low solute concentration to high.

Ah. Osmosis. That's the one. Of course.

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Osmosis is the phenomenon that allows you to draw liquid out of foods by sprinkling them with salt. It's what makes a country ham dry and the cabbage for your coleslaw tender-crisp and packed with flavor. It's a technique I use any time I'm going to incorporate a very moist vegetable, like cucumbers or tomatoes, into a chopped salad. Why not use it on my zucchini?

I cut my zucchini into thin matchsticks, then tossed it in a bowl with a big pinch of kosher salt, along with some minced garlic for extra flavor. I then placed the zucchini in a strainer and let it rest for half an hour.

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By the time I was ready to cook the pizza, I could see liquid dripping out of it. A big squeeze brought out a shower of juices. In fact, I was able to pull out over 30% of the zucchini's weight in excess water.

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Imagine taking all that liquid and pouring it right on top of your pizza when it's done cooking. That's essentially what's happening when you add zucchini to a pizza without first purging it of excess water.

This time of year, I typically bake my pizzas on the Baking Steel/KettlePizza Combo add-on for my Weber kettle, but the folks at Kalamazoo Gourmet lent me an outdoor gas-fired pizza oven to test out for the summer (stay tuned for a full review), so I fired it up.

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Now to find some partners in crime for the zucchini. I tried putting some of it directly on a red pie with mozzarella cheese, but the tomatoes were a little too overpowering for the delicately flavored zucchini. A second pie, made with halloumi cheese, thinly sliced onions, zucchini, and sumac, was a big hit—but my favorite combination was zucchini, mozzarella, feta cheese, thinly sliced garlic, and thinly sliced lemons, with some sliced scallions sprinkled on top after it came out of the oven.

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The salty, clean flavor of the feta goes well with the zucchini, while thin lemon slices add both tang and a touch of bitterness from the rinds.

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The finished pizza was pretty darn fantastic, especially since the zucchini lost even more moisture in the oven, its edges browning and sweetening up as the pie cooked.

I may have just found a new favorite pizza topping. And I think these guys did, too:

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(Yes, they got a special treat for dinner.)