01 - Grease a 9 x 13 inch baking dish thoroughly with butter or cooking spray to prevent sticking.
02 - Spread half of the bread cubes in an even layer across the bottom of the dish. Scatter cream cheese cubes and half the blueberries evenly over the bread. Top with remaining bread cubes and remaining blueberries.
03 - In a mixing bowl, whisk together eggs, milk, cream, sugar, and vanilla extract until fully combined and smooth.
04 - Pour the custard mixture evenly over the bread and berries, pressing gently with a spatula to ensure all bread pieces absorb the liquid. Cover and refrigerate for at least 30 minutes, or overnight for optimal flavor absorption.
05 - Preheat oven to 350°F.
06 - In a small bowl, combine softened butter, brown sugar, flour, cinnamon, and salt. Mix with a fork until the mixture resembles coarse crumbs.
07 - Sprinkle the streusel mixture evenly over the entire surface of the casserole.
08 - Bake uncovered for 40 to 45 minutes until the top is golden brown, the edges are bubbling, and the center is set and no longer jiggly.
09 - Allow the casserole to cool for 5 to 10 minutes before serving. Dust with powdered sugar if desired and serve warm.