Roughly mash the banana with a fork or something similar. Preheat the oven to 180°C. Line a muffin tray with muffin cups.
Cream the margarine with a whisk, then beat together with the sugar until it becomes white.
Add the egg, then the heavy cream and mix well. Then sift in the powder ingredients (cake flour, baking powder & cinnamon) and the mashed banana and mix lightly.
Pour the mixture from Step 3 into the muffin cups. You can use a curry spoon to help pour the mixture in evenly.
Mix 1 teaspoon sugar (not listed) into the cocoa powder followed by 1 teaspoon boiling water (also not listed). Dribble this over the muffins and mix lightly with a skewer to create the marble pattern.
Bake the muffins for 20-25 minutes at 180°C. Pierce with a skewer and if the skewer comes out clean, then the muffins are done!
Story Behind this Recipe
I made a muffin version of my "Marbled Banana Bread" (Recipe ID: 32388). I love the combination of bananas and cinnamon so I wanted to use that pairing in something.