A sweet-sharp buttermilk and mayonnaise dressing, mixed ahead and kept well away from the cabbage until the last minute.
Dressing ahead, slaw at the last minute
The dressing is better for a rest — at least 15 minutes, or covered in the fridge for up to two days. Do not dress the cabbage until you are ready to put it on the table.
In a medium bowl, whisk the mayonnaise, milk, cider vinegar, buttermilk, sugar, salt, pepper, celery seed, cayenne and lemon juice together until well mixed.
Give the dressing at least fifteen minutes for the flavours to come together. Covered in the fridge it keeps for two days, and it is better for the wait — but if you have no time, the slaw will still be good.
This is the part you can do the morning of.
Put the cabbage in a large bowl, add the yellow mustard and toss until every shred is coated.
Pour over the dressing and toss again, coating evenly. Taste, adjust, and serve.
Slaw wilts fast once it is dressed. Do this as it goes to the table, not an hour before. Dressed and tightly covered, it holds one day.