How to Make It
In a saucepan, combine the canola oil, ginger and lemongrass. Cook over moderately low heat until small bubbles appear around the side, 10 minutes. Let cool, then strain. In a blender or mini food processor, combine the mirin, rice vinegar, dry mustard and egg yolks; process until smooth. With the machine on, add the infused oil in a thin stream and process until emulsified. Season with salt and white pepper.
In a saucepan, combine the water, sugar, vinegar, coriander seeds, mustard seeds, crushed red pepper and bay leaf and simmer until the sugar has dissolved. In a heatproof bowl, carefully toss the melon balls with the brine and let cool.
In a bowl, mix 3/4 cup of the lemongrass mayonnaise, the scallions, basil, cilantro and the 1 1/2 cups of bread crumbs. Add the crab and season with salt and white pepper. Pat the mixture into 8 cakes about 3/4 inch thick; coat with bread crumbs. Set the cakes on a wax paper-lined plate.
In a nonstick skillet, melt 1 tablespoon of the butter in 1 tablespoon of the oil. Add half of the crab cakes and cook over moderately high heat, turning once, until golden, 6 minutes; drain on paper towels. Repeat with the remaining butter, oil and crab cakes. Set 2 crab cakes on each plate and add a dollop of the mayonnaise. Discard the bay leaf from the melon balls and serve in small bowls.