Shrimp and Crab Cakes with Wasabi Mayonnaise

Name: Shrimp and Crab Cakes with Wasabi Mayonnaise
Ingredients: 1 large egg; 1 scallion, thinly sliced, white and green parts, separated; 2 teaspoons finely grated freshly peeled ginger; 1 tablespoon soy sauce; 5 tablespoons low-fat or regular mayonnaise; 1 lime; 8 ounces jumbo lump crabmeat, drained and picked over for shells; 8 ounces bay shrimp, deveined and finely chopped; 4 tablespoons panko (Japanese breadcrumbs), plus up to 2 cups for breading; Freshly ground pepper; 1 tablespoon wasabi powder; 1/4 cup vegetable oil; Sprouts for serving, optional