Whisk together the melted butter, oil, caster sugar and brown sugar.
Add the egg and vanilla.
Whisk in the milk + coffee and yogurt.
Sift in the flour and baking powder to form a batter.
Fold in the toasted walnuts and transfer the batter into paper liners.
Bake at 180C for 18-20 minutes or until a skewer inserted in the middle comes out clean.
