Combine the Biga, butter and sugar in the bowl of your mixer with the paddle attachment at speed one for about thirty seconds. Add the flours and the gluten, switch to the dough hook, and mix until everything comes together in a rough ball. Add the salt at this stage. Knead for four minutes on speed two. Turn off the machine. The dough should be tacky, but not sticky. If it’s very sticky, briefly knead in more flour. If it’s too stiff and dry, dribble in a bit more water with the machine running. Switch off the machine, and take the dough’s temperature. Remember that your range is 77-81ºF. If you are on the low end, continue kneading for another minute or two. If on the high end, turn the dough out onto a lightly floured counter and knead by hand until the dough passes the windowpane test described in Chapter 2.