Line a 12-section bun tray with paper cake cases. Put the flours, baking powder and sugar in a bowl.
Whisk together the eggs, oil, melted butter, vanilla extract and yogurt with a fork in a jug and add to the bowl.
Mix gently with a large metal spoon until the ingredients have started to blend together. Scatter with half the berry pieces and mix a little more until the ingredients are only just combined. Divide the muffin mixture between the paper cases. Scatter with the remaining berry pieces.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 15 minutes or until well risen and just firm. Transfer to a wire rack to cool.