Ponzu: Combine all of the ingredients in a small, non-reactive saucepan. Bring to a boil. Remove from the heat, strain and discard zest. Keep warm.
Yuzu Vinaigrette: Whisk all of the ingredients together in a small mixing bowl and set aside.
Steaming Liquid: Place all of the ingredients in a large saucepan (large enough to keep the dashi kombu flat.) Bring to a boil over medium heat. Remove from the heat and set aside for 30 minutes. Remove the kombu and reserve both the liquid and the kombu.
Put the steaming liquid in the bottom of your steamer and bring to a boil. Cut the kombu in half. Place 1 sheet of the kombu on the perforated pan of your steamer. Arrange the skate wingson the kombu. Cover with the other piece of the kombu. Set the perforated pan over the boiling liquid, and cover with a lid. Steam for 4 or 5 minutes over high heat.
Meanwhile, cook the cabbage. Heat the oil in a sautepan, add the cabbage, and stir-fry until the edges of the cabbage just start to brown. Add the garlic and stir-fry for about 10 seconds. Remove from the heat and lightly season with salt and pepper.
Divide the cabbage among 4 large, hot serving bowls. Place a skate wing on each cabbage mound. Spoon the Ponzu over the skate. Toss the garnish greens together and then mound them on top of the skate. Sprinkle with the Yuzu vinaigrette and sesame seeds.