Zucchini Casserole

Ingredients (15)

• 2 pounds small/medium zucchini about 4 or 5 zucchini
• 3/4 teaspoon kosher salt divided
• 1 medium yellow onion
• 3 tablespoons unsalted butter divided
• 1/4 teaspoon ground black pepper
• 4 cloves garlic minced (about 4 teaspoons)
• 1/4 cup all-purpose flour
• 1 cup low-sodium chicken or vegetable broth
• 1/3 cup milk (I used 1%)
• 1/2 cup whole milk plain Greek yogurt about 1, 5-ounce container
• 3/4 cup shredded sharp cheddar cheese
• 4 tablespoons finely grated Parmesan divided
• 2 teaspoons chopped fresh thyme leaves or 1/2 teaspoon dried thyme
• 1/2 cup Panko breadcrumbs divided
• fresh herbs for serving like fresh parsley or basil, optional