01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Arrange half of the sliced croissants 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.
04 - Dollop or spread the cream cheese mixture over the croissants and berries in the dish.
05 - Layer the remaining croissants on top, followed by the remaining blueberries.
06 - In a separate bowl, whisk together eggs, whole milk, heavy cream, and 1/3 cup sugar until well combined and smooth.
07 - Pour the custard mixture evenly over the entire casserole. Gently press down on the croissants to help them absorb the liquid.
08 - Drizzle melted butter over the top. Let the dish stand for 10 minutes to allow the bread to soak up the custard.
09 - Bake uncovered for 35–40 minutes until golden brown and set. If the top begins to brown too quickly, cover loosely with foil during the last 10 minutes of baking.
10 - Let the casserole cool for 10 minutes before serving. Dust with powdered sugar just before serving, if desired.