Knead together 4 tbs. flour, yeast, 1/2 tbs. sugar, and 1 egg yolk, adding some warm water if necessary. Let rise, covered, in a warm draft-free place for a couple of hours, or until doubled in size. Knead the risen dough with 2 cups flour, 1 oz. softened butter, 2 oz. sugar and 2 yolks. Knead energetically for 15 mins. Let rise for another two hours or until it has doubled in size again.
Place the remaining flour, 2 tbs. butter, 4 tbs. sugar, 2 yolks, the whole egg and the fermented dough on the pastry board. Knead again for 20 mins. Let rise 2 hours for the third time. Take the dough again and knead in a pinch of vanilla, the grated lemon rind and 2 or 3 tsp. cream. When the dough is well mixed, roll into a 12x8-in. rectangle. Cut the butter into chunks, let it soften and place in the center of the dough.
Fold the dough back onto itself from both directions to make 3 layers and roll it out again. Let the dough rest for half an hour, fold again and roll out two more times, letting the dough rest in a warm place in between.
Butter and dust with sugar a deep mold, preferably a deep, star-shaped mold. Place the dough in the mold (it should fill it only halfway) and let rise until the dough reaches the upper rim of the pan. Cook in a pre-heated oven at 375°F. After 20 mins. reduce the temperature to 325°F and bake for another 20 mins.
