Preheat oven to 190°C. Grease or line 12 muffin cups with paper liners.
Combine bananas, yogurt and baking soda in a small bowl. Reserve.
Whisk egg, brown sugar, oil and vanilla in a medium bowl.
Add flour and baking powder to a separate large bowl.
Add reserved banana mixture and egg mixture to flour mixture.
Stir together until flour is incorporated into batter.
Spoon batter into prepared muffin pan.
Bake in preheated oven for 18-20 minutes or until a toothpick inserted in center of muffin comes out clean