Lightly grease a 9x13-inch baking dish with cooking spray or butter. Cut the day-old croissants into bite-sized pieces and evenly distribute them in the dish.

In a large bowl, whisk together the fresh orange juice, orange zest, granulated sugar, and eggs until blended. Add the whole milk, heavy cream, vanilla extract, ground cinnamon, and salt.

Pour the custard mixture over the croissants, ensuring they are well-soaked. Cover with plastic wrap and refrigerate for at least 1 hour, preferably overnight.

Preheat your oven to 350°F (175°C). This ensures the custard sets while the croissant tops brown nicely.

Remove the plastic wrap and drizzle melted butter over the top. Bake for 35-40 minutes until the top is golden brown and the custard is set.

While baking, whisk together powdered sugar and fresh orange juice until smooth for the glaze.

Once baked, drizzle with the orange glaze and garnish with orange slices and mint leaves before serving.