Use a fork to stir the chives, parsley, garlic, onion, black pepper, and sea salt into the mayonnaise.
Add kefir (or coconut milk if dairy free) to reach desired consistency. Cover and chill at least an hour, it’s better the next day.
This keeps for 6 days without the kefir, 14 days with it (the probiotic activity helps keep it fresh). Do not freeze, mayonnaise-based sauces do not hold up well in the freezer.