Zucchini and Squash Gratin

Name: Zucchini and Squash Gratin
Ingredients: 3 pounds yellow squash, cut 1/8-inch thick; 2 pounds zucchini, cut 1/8-inch thick; 3 tablespoons unsalted butter, plus additional for greasing; 1 medium yellow onion, minced; 1 medium clove garlic, minced; 2 large eggs, lightly beaten; 8 ounces sour cream; 1/3 cup mayonnaise; 4 ounces sharp white Cheddar, freshly grated; 1 teaspoon chopped fresh thyme; 10 fresh basil leaves, chiffonade; 2 teaspoons kosher salt; 1/4 teaspoon freshly ground black pepper; 3 tablespoons minced fresh flat leaf parsley; 32 butter crackers, crushed; 2 tablespoons unsalted butter, melted; 3 tablespoons grated Parmesan