Cube the bread into bite-sized cubes, about one inch in size. Aim for roughly 6 cups of cubed bread.

Grease a 9x13-inch baking dish with butter or non-stick spray and layer half of the cubed bread.

Sprinkle half of the mixed berries over the bread layer and then add remaining bread cubes and the rest of the berries.

In a large mixing bowl, whisk together the eggs, milk, heavy cream, sugar, vanilla extract, and cinnamon until well combined.

Gently pour the custard mixture over the bread and berries and press down lightly to ensure even soaking.

In a small bowl, mix together flour, brown sugar, and cinnamon. Drizzle in melted butter and stir until resembling coarse crumbs.

Sprinkle the prepared topping evenly over the surface of the casserole.

Allow the casserole to sit at room temperature for about 20 minutes and preheat your oven to 350°F (175°C).

Bake uncovered for 40-45 minutes until golden brown and slightly crisp. Check for doneness.

Let cool for 5 minutes, dust with powdered sugar, and serve warm with maple syrup or whipped cream.