Cut the butter and shortening into a small dice, then place them in the freezer while you prepare the rest of the ingredients. Place the all purpose flour, whole wheat pastry flour, salt, and sugar in the bowl of a food processor fitted with a steel blade, then pulse a few times to combin. Scatter the butter and shortening pieces over the top. Pulse 8 to 12 times, until the butter is the size of chickpeas. Some of the pieces will be small and others will be larger (about the size of a thumnail).