Mash the banana on a flat plate with a fork and set aside.
Whisk together the flour, baking soda, cinnamon and salt and set aside as well.
Whisk together the oil, sugar, milk, chickpea flour, water and rum until no lumps of chickpea flour remain.
Add the mashed banana and whisk until smooth.
Add the flour mixture to the wet ingredients and fold together but don’t overmix so as to prevent gummy muffins.
Fill the cups about 3/4 of the way up and sprinkle the streusel on top.
Bake for 25 to 30 minutes or until a toothpick inserted in the center of one of the muffins comes out clean.
Let them cool in the pan for 5 minutes and then transfer them to a wire rack to cool completely.