1 (.25 ounce) package active dry yeast
1 cup warm water (110 degrees F/45 degrees C)
1/4 cup white sugar
2 eggs
1/2 cup nonfat plain yogurt
1 teaspoon vanilla extract
1 tablespoon grated lemon zest
1/4 teaspoon salt
4 cups unbleached all-purpose flour
1/4 cup dried currants
1/4 cup raisins
1 tablespoon confectioners' sugar
1 tablespoon butter, melted (optional)