In a large bowl, whisk together the flours, baking powder and salt and set aside. On medium speed in a standing mixer
with whisk attachment, cream together remaining 8 tablespoons (110 grams) butter with the granulated sugar. Beat in the eggs, one a time, until well combined. Fold in the dry ingredients until smooth and then fold in the yogurt and mandarin zest
. The result should be a thick batter that’s easy to spread.