Preheat the oven to 180°C.
Place 16 muffin cases in 2 muffin trays.
In a large bowl add the flour, sugar, baking powder, bicarbonate of soda and salt, mix well.
In a smaller bowl, whisk the egg, oil, yogurt and vanilla extract.
Then mix into the dry ingredients.
Fold in the bananas, blueberries and white chocolate chips until evenly mixed.
Fill the muffin cases two thirds full with the mixture.
Bake for 22 – 25 minutes or until a cocktail stick inserted in middle comes out clean.
Cool for 5 minutes, then put on a wire rack to cool fully.
To make the white chocolate drizzle, melt the white chocolate in bowl over a pan of barely simmering water together with the oil.
Once the muffins are cool, drizzle the chocolate over the muffins with a spoon.
Allow the drizzle to set (if you can wait) and serve!