Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking dish.
In a large bowl, whisk together the eggs, milk, vanilla extract, cinnamon, and salt until well combined.
Add the quartered mini donuts to the egg mixture and gently fold until the donuts are evenly coated.
Pour the mixture into the prepared baking dish, spreading it out evenly.
Drizzle the maple syrup over the top and sprinkle with chocolate chips if using.
Bake in the preheated oven for 25-30 minutes, or until the casserole is set and lightly golden on top.
Allow to cool for a few minutes before slicing. Serve warm with whipped cream if desired.