Sprinkle the yeast over the water in a small bowl. Wait 5 minutes until the yeast has dissolved. Beat the eggs in a large mixing bowl and beat in the sugar, salt, and vanilla. Melt the butter and beat it in; then beat in the yeast mixture and finally stir in the flour. Beat the dough until it is smooth and elastic, either by hand in the bowl or in a heavy-duty mixer fitted with the dough hook on low speed, about 10 minutes.
Place the dough in a buttered bowl and turn it over so that the entire surface is buttered. Cover the bowl loosely with plastic wrap and allow the dough to ferment until it has doubled in bulk, about 2 hours. Turn the dough out onto a lightly floured work surface and fold it over on itself several times to deflate.
Butter a star-shaped pandoro mold and half fill the mold with the dough. Cover the mold loosely with plastic wrap and allow the nadalin to proof until the mold is filled.
Immediately invert the nadalin onto a rack and remove the mold. Paint the nadalin all over with the melted butter and allow it to cool completely. Keep it tightly wrapped in plastic at room temperature until serving time. Before serving, dust lightly with the confectioners’ sugar.
© 1990 Nick Malgieri. All rights reserved.