Using a sharp knife, cut the salmon into 1-inch pieces and transfer to the bowl of a food processor. Pulse until the fish is finely chopped. (Take care not to overprocess or salmon will become a paste.) Transfer to a mixing bowl and add the panko, 1/4 cup of the scallions, 2 tablespoons of the cilantro, minced ginger, egg, sambal oelek, garlic, 1/2 teaspoon of the salt, and 1 1/2 teaspoons of the soy sauce. Using a rubber spatula, mix gently but thoroughly to combine. Divide the mixture into 6 even portions and shape into patties about 4 inches wide and 3/4 inch thick. Transfer to a parchment-lined baking sheet and cover with plastic wrap. Refrigerate while you prepare the mayonnaise and slaw.

In a very small saucepan combine the remaining soy sauce and the sugar and cook until reduced to a syrup, 2 to 3 minutes. The soy-sugar mixture should coat the back of a spoon. Set aside to cool completely. When cooled, add 1 1/2 tablespoons of the soy glaze to the mayonnaise and refrigerate until ready to serve the burgers. (The remaining soy glaze may be kept indefinitely at room temperature and used to drizzle on grilled salmon or grilled tuna.)

Combine the purple and green cabbages, remaining 1/4 cup of scallions, the red onion, 1/4 cup of the vegetable oil, rice wine vinegar, remaining 2 tablespoons cilantro, sesame oil, remaining 1/2 teaspoon of salt, and crushed red pepper, and toss thoroughly to combine. Transfer to a serving bowl and sprinkle with the toasted sesame seeds. Refrigerate while you prepare the burgers.

Heat a large skillet over medium-high heat and add the remaining 2 tablespoons of oil. When the oil is hot, season both sides of the salmon burgers lightly with the kosher salt and add the burgers to the skillet and cook, turning once, until golden brown on both sides and the salmon is just cooked through, about 3 1/2 minutes per side. Serve the salmon on warm buns, garnished with the soy mayonnaise and the sesame slaw.