Eggplant Parmesan Dip

Name: Eggplant Parmesan Dip
Ingredients: 1 medium eggplant , trimmed and cut into 1/2-inch pieces (about 7 cups); 1 tablespoon kosher salt; 3 medium garlic cloves , unpeeled; 1 large yellow onion , peeled and quartered; 3 tablespoons olive oil , divided; 1 ounce Parmesan cheese , grated (about 1/4 cup), plus more for sprinkling; 1 ( 8 - ounce ) package pre-shredded low-moisture mozzarella cheese , divided; 1 cup jarred marinara sauce (such as Rao’s), or homemade; 1/4 cup seasoned panko breadcrumbs; 1 ( 10 - ounce ) baguette , sliced on an angle into 1/2-inch-thick slices; 4 tablespoons salted butter , melted; Fresh basil leaves , for garnish