Preheat the oven to 425ºF, and line a large baking pan with nonstick parchment paper.
Cut the salmon into 1-inch cubes and place in the freezer for 20 minutes. Once chilled, pulse in a food processor. Don’t overprocess—you want to retain some pieces of fish for texture.
Beat the egg in a large mixing bowl. Add the scallions, pickled ginger, wasabi powder, cilantro, lemon juice, soy sauce, breadcrumbs, salt and a sprinkling of pepper.
To test the meatball's flavor heat a small skillet over high heat. Break off a small amount of the mixture, flatten between your fingers and fry until cooked. Taste to check the seasoning and add more lemon, ginger or wasabi powder if necessary.
Mix the two types of sesame seeds together and spread them out on a plate. Form the salmon mixture into 12–16 balls, each about 2 inches in diameter, packing each one firmly. Roll the balls in the sesame seed mixture and place them on the prepared baking pan.
Bake on preheated oven at 350 degrees for about 20 minutes or until the meatballs are browned and cooked through. Careful not to overcook.