Using a whisk, cream the egg yolks and maple sugar in a bowl until light and fluffy. Then use a spatula to blend in the dry ingredients, which were sifted together beforehand, and the softened butter. Mix just until the texture is uniform.
Remove the dough from the bowl and shape into rolls about ¾ inch (2 cm) in diameter using plastic wrap. Chill in the refrigerator for at least 4 hours.
Preheat oven to 325° F (160° C).
Remove the plastic wrap and cut the rolls into slices about ½ inch (1.5 cm) thick. Place the slices in a non-stick muffin pan and bake for 20 minutes. Let stand 5 minutes before removing from the pan. Then cool completely on a wire rack.