Chef’s Mushroom Lasagna

9 lasagna noodles-1 (15-ounce) package whole milk ricotta-2 (10-ounce) packages frozen chopped spinach, thawed and drained-3 cups shredded mozzarella cheese, divided-3/4 cup freshly grated Parmesan, divided-2 tablespoons chopped fresh parsley leaves

FOR THE SAUCE

-1/4 cup unsalted butter-2 cloves garlic, minced-1 pound cremini mushrooms, thinly sliced-1 onion, diced-1/4 cup all-purpose flour-3 cups milk, at room temperature-1 teaspoon dried basil-1/2 teaspoon dried oregano-Pinch of nutmeg-Kosher salt and freshly ground black pepper, to taste