Sableuse
A very buttery and rich cake.

Preheat oven to 350°F. Butter and line bottom of 8” square pan, then butter paper.

In stand-up mixer, whisk the yolks and the whole egg with sugar at medium speed until pale yellow in color and light and fluffy, about 15 minutes. Sift dry ingredients. Gradually add into the yolk mixture on low speed, by tablespoons, and adding more when the previous addition is thoroughly blended. Increase speed to medium and pour in butter in 3 batches. After second is added and mixed in, turn off machine and remove bowl from mixer. Fold in last addition of butter by hand. Pour the batter into pan. Wrap the pan completely with two sheets of foil. Fold loosely at top to allow for expansion. Bake for 40 minutes or until cake has risen and springs back. Remove from oven and immediately unmold onto plate. Peel off parchment and turn cake right-side up. Cool to room temperature and serve.