Preheat oven to 180℃.
Line a 12-hole muffin pan with paper liners and set aside.
In a large bowl, whisk together the flour, light brown sugar and cinnamon, then stir in the chocolate chunks and set aside.
270 g self-raising flour, 155 g light brown sugar, ¼ teaspoon ground cinnamon, dark chocolate
Place bananas in a medium bowl and mash until smooth.
3 overripe bananas
Add buttermilk, vegetable oil, melted butter, beaten egg and vanilla extract to the banana puree and mix well to combine.
250 ml buttermilk, 2 tablespoons vegetable oil, 60 g salted butter, 1 egg, 1 teaspoon vanilla extract
Pour the banana mixture into the flour mixture and fold gently to combine - it's important not to overmix so the muffins stay soft.
Divide the batter evenly among the holes of the lined muffin tin.
Bake for 20-25 minutes, or until a skewer or toothpick inserted into the middle of a muffin comes out clean.
Remove muffins from the pan and place on a wire rack to cool.