Blend graham crackers in a food processor until fine crumbs. Mix with melted unsalted butter, kosher salt, and cinnamon until resembling wet sand, then set aside.

Whisk cornstarch and water until combined. In a saucepan, combine raspberries, sugar, and lemon juice, mixing until berries are coated. Add cornstarch mixture and cook over medium heat, mashing lightly. Bring to a boil for about 3 minutes until thickened. Set aside to cool.

Preheat oven to 350°F (175°C) and prepare baking dish with nonstick spray.

In a bowl, whisk together vanilla Greek yogurt, eggs, egg yolk, honey, and vanilla extract until smooth. Sift in cornstarch and mix thoroughly.

Pour yogurt mixture into baking dish. Gently fold in mixed berries if using. Bake for 35-38 minutes until the center is firm.

Cool for 20 minutes at room temperature before serving with graham cracker topping and berry sauce.