Preheat oven to 350 degrees F. In the bowl of a stand mixer with the paddle attachment, add the flours, sugar, butter, lemon zest and a pinch of salt. Mix on medium speed until the dough starts to form. Add the 4 egg yolks, 1 at a time, and mix briefly, just to incorporate. Spoon the dough onto a piece of parchment paper and roll into a log shape. Let the dough rest in the refrigerator for 30 minutes.
|