Preheat your oven to 175°C / 350°F. Butter a medium baking dish (about 8x10 or similar).
Add half of the cubed sourdough to the baking dish. Scatter over half of the sliced bananas and half of the chopped dates. Add the remaining bread, bananas, and dates on top.
Melt the butter and drizzle it over the pudding.
In a large bowl, combine eggs, milk, cream, sugar or honey, cinnamon, cardamom, nutmeg, salt and vanilla (if using). Whish until smooth.
Slowly and evenly pour the custard over the bread mixture in the baking dish. Gently press the bread down with the back of a wooden spoon so it absorbs the custard. Sprinkle the pudding with a tablespoon or two of brown sugar if you like a crispier topping.
Let the pudding sit for 15 minutes to soak.
Bake uncovered for about 35 minutes until the custard is set but still slightly soft in the middle, and the top is golden.
Let it rest for 10 minutes, then serve warm with a drizzle of cream or warm milk.