Preheat the oven to 200 C / Gas 6. Grease a muffin tin or line with paper cases.
Sift the flour, baking powder and cinnamon into a bowl and stir in the sugar. Whisk together the oil, yoghurt, milk and eggs and add to the flour mixture. Stir in the pecans and mashed bananas, then pour the mixture into the prepared cases.
Bake for 20 minutes or until the muffins are well risen and a skewer inserted in the centre comes out clean.