In a large bowl mix together the sour cream, mayonnaise, milk, scallions, and jalapeno. Season generously with salt and pepper. Add the red onion and cabbage and toss to blend well. Taste and adjust the seasoning.
Notes
You could always try adding cilantro, cumin and green or jalapeno pepper for a Tex-Mex style slaw; coriander, fennel seeds, curry powder and onion for an Indian take; Glass noodles, seedless cucumber and firm-ripe mango with a cayenne, lime and rice vinegar dressing for a Vietnamese twist.