Make dressing one day or a few hours before serving: Combine first seven ingredients (lime juice through black pepper) in a one-cup measuring glass or bowl. Add olive oil and whisk until emulsified. Place in refrigerator until serving.*
In a large serving bowl, combine the cabbage, carrots, onion and herb of choice, if using. Add the prepared dressing and toss well until everything is coated.
Notes
*Make entire salad up to a day ahead by prepping slaw ingredients at the same time as the dressing and keeping it all in the fridge until you need it.