Step 1: Grease a 9x13 inch baking dish with butter or non-stick spray. Place the cubed bread evenly into the dish.
Step 2: In a large mixing bowl, whisk together the eggs, milk, heavy cream, granulated sugar, and vanilla extract until well combined.
Step 3: Pour the egg mixture evenly over the bread cubes. Use a spatula to lightly press down on the bread to ensure it is all soaking in the liquid. Cover with foil or plastic wrap and refrigerate for at least 4 hours, or preferably overnight.
Step 4: When ready to bake, preheat your oven to 350°F (175°C). In a small bowl, mix the flour, brown sugar, cinnamon, and salt for the topping. Cut in the cold butter using a pastry blender or your fingers until the mixture resembles coarse crumbs.
Step 5: Remove the dish from the refrigerator and sprinkle the streusel topping evenly over the soaked bread. Bake for 45-50 minutes until the top is golden brown and the center is set. Serve warm with maple syrup.