To make a fresh crab salad, gently combine 1 pound of cleaned jumbo lump crab meat with 4 teaspoons of sliced fresh chives in a bowl. Fold in a stalk of finely diced celery and 1 teaspoon of minced fresh tarragon leaves. Mix lightly until the ingredients are just blended.
In a separate bowl, mix 1/3 cup of mayonnaise with 3 tablespoons of sour cream, 1 teaspoon of fresh lemon juice and 1/2 teaspoon of Dijon mustard. Combine the dressing and crab mixtures until the crab is lightly coated. Season the crab salad, to taste.
To make a crab salad with paprika-scallion mayonnaise, place 1/2 cup of finely chopped sweet onion in a large mixing bowl. Top the onion with 1 pound of jumbo lump crab and season the crab with salt and pepper, to taste. Add another 1/2 cup of chopped sweet onion over the crab.
In a separate bowl, whisk 1/2 cup of peanut oil together with 1/2 cup of ice water and 1/3 cup of apple cider vinegar. Pour the mixture over the crab, cover and marinate overnight in the refrigerator.
In a medium bowl, combine 3/4 cup of mayonnaise, 1 tablespoon of fresh lemon juice, 1 tablespoon of apple cider vinegar and 1/4 teaspoon of sweet paprika. Drain the crab and fold it into the mayonnaise mixture. Stir in 1/4 cup of coarsely chopped flat-leaf parsley and 2 tablespoons of thinly sliced scallions.
Garnish the crab salad with thin slices of red onion and serve.