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 in the bottom of the prepared dish and scatter half of the blueberries on top.
03 - In a medium bowl, beat together cream cheese, 1/2 cup sugar, and vanilla until smooth and creamy. Dollop or spread the mixture over the croissants and berries.
04 - Layer the remaining croissants and blueberries on top of the cream cheese mixture.
05 - In a separate bowl, whisk together eggs, milk, heavy cream, and 1/3 cup sugar until well combined and smooth.
06 - Pour the custard evenly over the casserole, pressing the croissants gently to help them absorb the liquid. Drizzle melted butter over the top. Let stand for 10 minutes to allow soaking.
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. Serve warm for best results.