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