For crusts:

• 4 cups finely ground graham cracker crumbs (about 32 crackers)
• 6 ounces (12 tablespoons) unsalted butter, melted
• 2 tablespoons granulated sugar
• 1/4 cup (packed) light-brown sugar
• 1 teaspoon coarse salt
• 1 teaspoon ground cinnamon
• 6 ounces bittersweet chocolate (preferably 61 percent cacao), finely chopped

For filling:

• 12 ounces semisweet chocolate (preferably 55 percent cacao), chopped
• 4 ounces (6 tablespoons) unsalted butter, cut into small pieces
• 1 can (15 ounces) solid-pack pumpkin
• 1 can (12 ounces) evaporated milk
• 3/4 cup packed light-brown sugar
• 3 large eggs
• 1 tablespoon cornstarch
• 1 teaspoon pure vanilla extract
• 1 1/2 teaspoons coarse salt
• 3/4 teaspoon ground cinnamon
• 3/4 teaspoon ground ginger
• 1/4 teaspoon ground nutmeg
• Pinch of ground cloves

For topping:

• 2 ounces milk chocolate, melted