Cream butter in the bowl of a stand mixer fitted with the paddle attachment till light and fluffy. In a separate bowl, whisk the egg yolks with the sugar till light. Gradually add this into the butter and beat on medium speed till just incorporated. In a separate bowl, with a hand mixer, whisk the egg whites till stiff peaks form. With a spatula, fold in the meringue into the egg yolk mixture in 3-4 batches. Add in the dry ingredients gradually until just incorporated.