Preheat the oven to 180°C/350°F fan setting.
Mix the softened butter with the granulated sugar.
Add in the maple syrup, lightly beaten egg, natural yogurt and vanilla extract.
Stir in the dry ingredients, the flour, baking powder and salt.
Wash a punnet of blueberries (about 125 grams) and pat them down until completely dry. Sprinkle the blueberries with a little plain flour until coated and then stir into the batter gently, together with the white chocolate chips.
Pour the batter into a greased oven dish about 10 x 10 inch (or 25 x 25cm). Sprinkle with some extra chocolate chips.
Bake in the middle shelf of the oven for about 20 minutes or until the edges are slightly golden but the middle is still soft.
Remove from the oven and let it cool completely before cutting into squares.
If you like you can mix some icing sugar with milk or water and drizzle this over the top in diagonal lines to finish.