Gather all ingredients and preheat your oven to 350°F (175°C). Generously coat a 9x13-inch baking dish with nonstick cooking spray.
In a large mixing bowl, whisk together the eggs, milk, heavy cream, brown sugar, vanilla extract, cinnamon, and salt until thoroughly combined.
Submerge each croissant half into the egg mixture, allowing it to soak fully.
Arrange the soaked croissants in the prepared baking dish, overlapping them as needed. Pour any remaining custard mixture over the layered croissants.
Bake in the preheated oven for about 30 minutes, or until the top is golden and a knife inserted in the center comes out clean.
Allow the dish to rest for 15 minutes before serving. Serve with your choice of toppings, such as fresh berries, powdered sugar, or a drizzle of maple syrup.