Preheat oven to 350°F (175°C) and grease a 9x13 inch baking dish.
Spread half of the croissant cubes evenly across the bottom of the prepared baking dish.
In a mixing bowl, beat the softened cream cheese and granulated sugar until smooth, then incorporate one egg and vanilla extract.
Dollop and spread the cream cheese mixture over the first layer of croissants.
Distribute 1 cup of fresh blueberries over the cream cheese layer.
Cover with the remaining croissant cubes and sprinkle the remaining 1 cup of blueberries on top.
Whisk together the milk, second egg, and ground cinnamon; pour the mixture evenly over the entire casserole.
Bake for 35 to 40 minutes until the custard is set and the croissants are golden brown.
Allow the casserole to rest for 10 minutes, then dust with powdered sugar before serving.