Finely chop the dill pickles and onion, if using. The finer you dice them, the smoother your sauce will be.
In a medium bowl, combine the mayonnaise, chopped pickles, fresh dill or parsley, lemon juice, sugar, and black pepper. Stir until well blended and creamy.
Taste the sauce and adjust as needed. Add more lemon juice for brightness or extra pickles for crunch.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes to allow flavors to meld.
Notes
Chill overnight for best results.
Store in an airtight container for about a week.
This sauce can also be served with vegetables or used as a sandwich spread.