This garlic mayonnaise recipe courtesy of Scott Peacock will be a great addition to any soft-shelled crab dish.
Coarsely chop garlic, and gather into a pile. Sprinkle with a pinch of salt. Place flat side of knife blade on top of garlic, with sharp side of blade away from you; press down firmly while pulling knife toward you. Repeat until a paste forms; place in a small bowl. Add boiling water and let stand 1 minute. If mixture is still chunky, strain through a fine mesh sieve and discard any chunks; set aside.
Whisk together vinegar, lemon juice, 1 teaspoon sea salt, and dry mustard in a nonreactive bowl until salt and mustard are dissolved. Add egg yolks and beat until smooth. Add oil, drop by drop, and then in a slow, steady stream, whisking constantly until emulsified. Stir in garlic paste. If mayonnaise seems too thick, add a little more hot water until desired consistency is reached.