2-1/2 pounds zucchini (or zephyr or patty pan summer squash)
2-1/2 teaspoons kosher salt (I use Diamond brand, use 1 1/2 of other brands)
1/2 cup plain, uncooked white rice
1 medium onion, minced (about 1 cup)
5 tablespoons olive oil, divided
2 large cloves garlic, mashed or finely minced
2 tablespoons all-purpose flour
Milk, as needed, although broth of your choice would work just fine
2/3 cup grated Parmesan cheese, divided
Salt and pepper
Butter for dish
Prepare zucchini: Wash zucchini and trim ends. Halve lengthwise, and if seeds are particularly large, core them out. Coarsely grate and place in a colander set over a bowl. Toss with kosher salt. Let drain for 5 minutes, says Julia Child, but more like 20 or, if you’ve got the time, up to 30 minutes.
Save drained liquid and squeeze a handful of the zucchini and taste. If it’s very salty, rinse and drain it again (not saving liquid this time). Squeeze all of the zucchini in handfuls, gently, collecting any juices in the bowl of drained liquid. Blot dry on paper towels.
Prepare rice: Boil for exactly 5 minutes in salted water. Drain and set aside. [In comments I’ve read about this recipe online, many people say that they skip this step and it all works out in the oven. But I didn’t this time.]
Prepare remaining ingredients: In a large frying pan, cook the onions slowly in 3 tablespoons oil for 8 to 10 minutes until tender and translucent. Raise heat slightly and stir several minutes until very lightly browned. Stir in the grated and dried zucchini and garlic; season with salt and pepper. Toss and turn for 5 to 6 minutes until the zucchini is almost tender. Sprinkle in the flour, stir over moderate heat for 2 minutes, and remove from heat.
Assemble dish: Measure the drained liquid from the zucchini. If you have less than 2 1/2 cups, add milk to bring the level up to it. Stir into zucchini-onion mixture, return pan to stove over medium-high heat and bring to a simmer, stirring. Remove from heat again, stir in par-cooked rice and all but 2 tablespoons cheese. Taste and adjust seasoning if needed.
Turn into a 2-quart baking dish, or 2 smaller 1-quart dishes (as I did, with the intention of freezing one). Sprinkle with reserved cheese and remaining olive oil.
You can cook it right away, or let it sit until 30 minutes before you want to serve it.
30 minutes before serving: Heat oven to 425 degrees. Bake in upper third of oven until bubbling and browned on top, about 25 to 30 minutes. (If yours begins to brown too quickly, you can cover it with foil until the last 5 minutes.) The rice should absorb all the liquid. Serve immediately.