Rehydrate the Seaweed

Place the dried wakame in a small bowl. Heat a large pot of water until it reaches a vigorous boil, then pour enough of it over the wakame to submerge it by at least two inches. Allow the seaweed to soak for approximately 10 minutes, then drain and cool in a colander. Set aside.

Cook the Noodles

While the wakame is soaking, prepare the udon noodles according to the package directions. Once cooked, drain them in a colander and rinse with cool water to halt further cooking.

Prepare the Dressing

In a mixing bowl or measuring cup, whisk together the sesame oil, canola oil, rice wine vinegar, mirin, soy sauce, and sweet miso until the mixture is smooth and emulsified. Set the dressing aside.

Toast the Sesame Seeds

If using sesame seeds, lightly toast them in a dry skillet over medium-low heat until aromatic, being careful not to burn them. Remove from heat and set aside.

Assemble the Salad

In a large serving dish, combine the drained noodles with the rehydrated wakame. Drizzle approximately three-fourths of the dressing over the mixture and toss gently to coat. Portion the salad into four bowls, topping each with the tuna, scallions, and a sprinkle of furikake or the toasted sesame seeds. Drizzle the remaining dressing over the top before serving.