Zucchini Rice Gratin

This French zucchini rice gratin is based on Julia Child's tian de courgettes au riz, and is a delicious side dish made with fresh summer squash, rice and cheese.

I've been polling my friends with the same question over and over again.

"What do you do when you've got too much zucchini?"

Most years, I use my zucchini and yellow squash to make this vegan ratatouille or this baked zucchini and squash, and that's about it.

This year, however, I found myself with an overwhelming amount of zucchini.

And so, after numerous amounts of friendly advice and suggestions, as well as perusing all my cookbooks, I decided to make a zucchini gratin. It's basically the French version of a cheesy zucchini casserole.

Follow along with my Instagram stories to see what I do with the rest of the zucchini!

This zucchini rice gratin is based on Julia Child's recipe for tian de courgettes au riz from her cookbook Mastering the Art of French Cooking, Volume II.

My version is an (ever-so-slightly) simplified version of Julia Child's recipe, and will walk you through some tips and tricks on how to use what you have on hand to make this savory and filling summer side dish.

This is not a complicated dish, but there are quite a few different components of the recipe to prepare before you actually start cooking. I recommend reading through the entire recipe in full before you start cooking.

How Much Zucchini Do I Need for This Gratin?

You need about two pounds of zucchini or yellow squash.

I use an analog kitchen scale to weigh my veggies, but if you don't have one, estimate four medium or six small squash.

How to Grate Zucchini

Start by grating your zucchini.

I used the large side of my Joseph Joseph grater, but you could also chop the zucchini in a food processor.

How to "Sweat" Zucchini

Next, place the grated zucchini in a large mesh sieve, and then set the mesh sieve over a large bowl.

Sprinkle the zucchini with salt, and stir or toss to mix the salt all through the grated veggies.

Let the zucchini rest for about five minutes, and then use your hands to squeeze as much liquid as possible out of the zucchini and into the bowl below.

When you squeeze and not much liquid comes out, you're ready to move on. The zucchini will still look and feel damp, but it's released most of the liquid.

Move the zucchini onto a towel to dry.

It won't get completely dry, but that's okay.

Reserve the zucchini liquid for later; don't discard it!

If your zucchini didn't release much liquid, or if you accidentally throw out this liquid, I'll have tips for you later. Keep reading.

Preparing the Rice

Next, you're going to parboil rice.

Bring a medium pot of water to a boil, and add white or jasmine rice. Don't use quick-cook rice, because it will turn to mush.

When you add the rice to the pot, set a timer for five minutes.

After four minutes, begin ladling some of the starchy rice water out of the pot and into the zucchini liquid. Keep going until you have two cups of liquid.

After five minutes, strain out the rice and discard the remaining rice water.

Can I Swap the Rice for Cauliflower Rice?

No, and don't skip the rice altogether either.

In this recipe, rice does something really important. The rice absorbs all the liquid you'll be pouring into the gratin.

Cauliflower rice won't absorb liquid, it will add more liquid. I love cauliflower rice, but do not use it in this recipe.

Zucchini + Rice Water Substitutions

If your zucchini were a little bit old, they might not have as much liquid to release. What should you do then?

What happens if you accidentally strain the rice without saving rice water?

Do not panic: you have options!

For this recipe, you simply need two cups of flavorful liquid. If you don't want to (or can't) use zucchini juices and rice water, you can swap equal amounts of warm milk or broth.

Can I Use Pre-Cooked, Leftover Rice?

For the best texture, I recommend cooking the rice as directed in the recipe.

If your rice is completely cooked before making the gratin, you risk over-cooked, mushy rice.

That said, if you want to experiment with pre-cooked rice, I recommend sticking to sturdier rice (like brown rice). Keep in mind that you'll need to use one of the rice-water liquid substitutions listed above.

What Size Pan Should I Use?

Start with a large, oven-safe pan. I used my Lodge 12" carbon steel skillet.

Do not use a smaller pan, the gratin ingredients will not fit.

If you don't have an oven-safe pan large enough, use whatever large pan you have, and transfer the gratin ingredients to a casserole dish before baking.

How to Make Zucchini Rice Gratin

Once your zucchini is salted and dried, your rice is parboiled, and you have two cups of liquid ready, it's time to move on.

Begin by cooking a diced onion until it begins to brown.

Next, add the grated zucchini.

Cook it for a few minutes, or until the zucchini becomes tender.

Add some flour to the pan, and stir to combine. All-purpose gluten-free flour (such as Cup 4 Cup) will work perfectly here.

The zucchini mixture will quickly begin to thicken. Make sure all the flour has been incorporated before moving onto the next step.

Next, begin slowly pouring the warm liquid into the pan. Stir as you pour, and continue adding until you've added all two cups.

Bring the liquid to a simmer.

Next, stir in the rice.

Add most of the cheese.

If needed, you can stop at this point and hold the gratin in the fridge for up to a day.

This zucchini rice gratin tastes best right after baking.

If you plan on moving the gratin to the fridge, I suggest using a larger pan than I did to avoid spills in the fridge, or transfer it to an easier-to-store lidded casserole dish.

Just before baking, sprinkle the remaining cheese on top.

Slide the gratin into the oven and bake for about 30 minutes, or until the top is golden.

Serve this gratin along with some baked tomatoes, pan-seared halibut, and a glass of crisp hard cider.