Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with butter or non-stick spray.
Tear the croissants into large pieces and evenly distribute them in the prepared baking dish.
In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, granulated sugar, vanilla extract, ground cinnamon, and salt until well combined.
Pour the egg mixture evenly over the torn croissants, ensuring all pieces are soaked. Gently press down the croissants to help them absorb the liquid.
Sprinkle the chocolate chips and sliced almonds (if using) over the top of the croissant mixture.
Cover the baking dish with aluminum foil and let it sit for about 30 minutes to allow the croissants to soak up the custard.
After 30 minutes, remove the foil and bake in the preheated oven for 30-35 minutes, or until the top is golden brown and the custard is set.
Let the croissant bake cool for about 10 minutes before serving. Dust with powdered sugar if desired.