By Hand, Add the fruit mixture, honey, egg, butter, zest, salt, mace, walnuts, and 2 cups of the flour to the sponge. Beat vigorously for 2 minutes. Gradually add the remaining flour 1/4 cup at a time until the dough begins to pull away from the side of the bowl. Turn the dough out onto a floured work surface. Knead, adding flour a little at a time, until the dough is smooth and elastic.