With the mixer still running, gradually add only enough of the reserved flour, one tablespoon at a time, to make a soft dough. If using a stand mixer, knead the dough with the dough hook for 5-6 minutes. If kneading by hand, transfer the dough on to a lightly floured work surface and knead for about 8-10 minutes (you may or may not use all the flour). In the latter case, the dough will be ready when it easily pulls away from your hands and the work surface and it's smooth and elastic (and still a tad sticky). Shape the dough into a ball and move on to point 8.