01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Slice croissants into 1-2 inch pieces. Arrange half of the croissant pieces in the bottom of the prepared dish. Scatter half of the blueberries evenly over the croissants.
03 - In a medium bowl, beat together cream cheese, 1/2 cup sugar, and vanilla extract until smooth and creamy. Dollop or spread the mixture evenly over the croissant and berry layer.
04 - Layer the remaining croissant pieces and blueberries on top of the cream cheese filling, distributing evenly.
05 - In a separate bowl, whisk together eggs, whole milk, heavy cream, and 1/3 cup sugar until well combined. Pour the custard mixture evenly over the casserole, pressing the croissants gently to ensure they soak up the liquid.
06 - Drizzle melted butter over the top of the casserole. Let stand for 10 minutes to allow the croissants to absorb the custard.
07 - Bake uncovered for 35-40 minutes until golden brown and set. If the top browns too quickly, cover loosely with foil during the last 10 minutes of baking.
08 - Let cool for 10 minutes before dusting with powdered sugar and serving warm.