Quarter the cabbage by cutting down into the core. Turn each quarter on its side and cut down the edge of the solid core to remove and discard it. Peel off the outer leaves and discard as well. Cut into 1-inch chunks and, working in batches, fill a food processor with cabbage to the halfway point. Pulse six times, then run the food processor continuously for 30 to 60 seconds until the cabbage is finely chopped. Stop short of a minced paste. Place the chopped cabbage in a bowl large enough to allow some serious mixing.In a separate bowl, mix together the sugar, mayonnaise, salad dressing, and mustard until fully combined. Pour over the chopped cabbage, mix well, cover with plastic wrap, and refrigerate.This slaw is best once it sits for several hours (that’s when the precious juice rises to the top), but it’s also ready to eat immediately if need be. The slaw is best the day-of because it loses its crispness over- night, but it will keep in the refrigerator for 2 days.