Place bananas, milk and cinnamon in a blender and blend until smooth.
Pour banana mixture through a fine mesh strainer into a medium saucepan. Add chocolate and heat, whisking frequently, until chocolate is completely melted and the mixture is smooth and velvety.
Remove from heat. Add rum, if adding. Serve immediately with a dollop of whipped cream on top.
Recipe by Port and Fin at https://portandfin.com/banana-hot-chocolate/