Zucchini Cheese Gratin

This is a Julia Child's recipe from Mastering the Art of French Cooking--so it goes way back, and there have been some modern updates that make it even easier.Some parboil the rice, but all I did was soak it until I was ready to assemble and it worked beautifully. The other great thing about this recipe is that it uses grated zucchini, and a lot of it. I had an over-sized zucchini (who can help it when they grow 5-6 inches a day, I ask you?) and it was only a pound and a half, so I had to add more. So a bonanza for using those big ones that does not involve making zucchini cake with them. Butter for dish 2 1/2 pounds (about 1 1/8 kg) zucchini 2 1/2 teaspoons kosher salt (I use Diamond brand, use 1 1/2 of other brands) 1/2 cup (90 grams) plain, uncooked white rice 1 medium onion, minced (about 1 cup) 5 tablespoons (75 ml) olive oil, divided 2 large cloves garlic, mashed or finely minced 2 tablespoons (15 grams) all-purpose flour (optional) 1/2 cup milk, as needed, although water or broth of your choice would work just fine [1/2 cup needed for streamlined directions, less for original] 2/3 cup (55 grams) grated Parmesan cheese, divided Salt and pepper DIRECTIONS: Heat oven to 425 degrees F. Oil or butter a 2-quart baking dish, or 2 smaller 1-quart dishes (as I did, with the intention of freezing one). Prepare zucchini: Wash zucchini and trim ends. Halve lengthwise, and if seeds are particularly large, core them out. Coarsely grate and place in a large bowl. 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 garlic and cook another minute. Add uncooked rice that you have soaked in water then drained, and sauté for another two minutes. Season generously with salt and pepper. Assemble gratin: Transfer to bowl with zucchini and stir together with 1/2 cup liquid of your choice (I used cream because that was what I had and they suggest whole milk). Taste and adjust seasoning if needed. Transfer to prepared baking dish. Bake gratin: Turn into a 2-quart baking dish, or 2 smaller 1-quart dishes. Bake uncovered at 425. For extra color, you can run it under the broiler for one minute at the end. You can cook it right away, or let it sit until 30 minutes before you want to serve it.