Preheat your oven to 350°F.
Grease and flour a 6-cup muffin tin.
Puree the dates using a blender or immersion blender.
Pour the mixture directly into a bowl.
In a separate bowl, mix the dark brown sugar, unsalted butter, and egg.
Combine until smooth.
Add the plain flour and baking powder to the mixture.
Mix until fully combined.
Gently fold in the pureed dates and sliced banana.
Mix until evenly distributed.
Divide the batter evenly between the prepared muffin tin cavities.
Place the muffin tin in the oven and bake for 17-19 minutes.
Check for doneness with a toothpick.
In a separate saucepan, melt the caster sugar until it caramelizes.
Stir in unsalted butter for a rich toffee sauce.
Serve the warm puddings with the toffee sauce drizzled over the top.