Preheat the oven to 350°F (175°C) and grease a 9x13 inch baking dish.
Cut the bread into cubes and layer half of the cubes in the prepared baking dish.
Sprinkle half of the mixed berries over the bread cubes.
Layer the remaining bread cubes on top, followed by the remaining berries.
Whisk together the eggs, milk, sugar, vanilla extract, cinnamon, and salt until well combined.
Pour the custard mixture evenly over the layered bread and berries.
Press down gently to ensure the bread absorbs the custard.
Cover the dish with foil and bake for 30 minutes.
Remove the foil and bake for an additional 15 minutes, or until golden brown on top.
Let cool slightly before serving with whipped cream and a dusting of powdered sugar.