1-Preheat the oven to 350°F (180°C), or 160°C for a fan oven. Grease a 9×13 inch baking dish with the softened butter.

2-Cut the croissants into 1-inch pieces and place them in the greased baking dish.

3-In a bowl, whisk together the 6 large eggs, 1 cup whole or 2% milk, 1 cup heavy whipping cream, ¼ cup granulated sugar, 1 teaspoon pure vanilla extract, ½ teaspoon cinnamon, and ¼ teaspoon salt until fully combined.

4-Pour the custard mixture over the croissant pieces and let it sit at room temperature for 20 minutes to soak. Alternatively, cover and refrigerate overnight if preparing ahead.

5-Cover the dish with foil and bake for 30 minutes. Remove the foil and bake for another 10-15 minutes until golden brown and the custard reaches an internal temperature of 160°F (70°C).

6-Serve warm or at room temperature, topped with vanilla sauce or crème anglaise and fresh berries if desired.