I've found through tinkering that the following is delicious:
1 cup mayo
1 tbsp parsley or chives(fresh and chopped)
1 tbsp vinegar(white or cider)
1-2 cloves garlic(depending how strong you like it) Freshly minced garlic only or it will not be the same.
1 tbsp of milk or cream(thins out the mayo a bit.)
1 tbsp spicy, brown mustard or 1 tsp ground mustard
1 tsp sugar
Salt and freshly cracked pepper (to taste)
Mix all the ingredients and you’ll end up with just over a cup. To get your desired thickness you may have to play around with the ratio of mayo to milk. It's not very healthy but it's great on a salad or as a dip.