Makes 5 dozen
1 pound very fresh yellowfin tuna steak, cut into ¼ inch dice
3 tablespoons snipped fresh chives
2 tablespoons sesame oil
¼ cup low-sodium soy sauce
2 tablespoons rice wine vinegar
½ teaspoon kosher salt, or more to taste
¼ teaspoon freshly ground black pepper, or more to taste
¼ cup homemade or prepared mayonnaise
1 teaspoon chili paste
3 Japanese or Kirby cucumbers
1 teaspoon black sesame seeds, toasted.
In a medium bowl, combine the tuna, chives, sesame oil, soy sauce, vinegar, salt, and pepper. Cover tightly with plastic wrap and refrigerate.
Mix the mayonnaise and chili paste in a small bowl, cover and refrigerate.
Using a mandoline, slice the cucumbers lengthwise as thinly as possible into approximately 5-inch lengths. Season with salt and pepper to taste. Place 1 heaping teaspoon of tuna tartar on one end of the cucumber slice. Roll up. The cucumber, when very thinly sliced, will stick together and stay rolled without a toothpick Continue making rolls with the remaining ingredients.
Fill a pastry bag fitted with a small (#3 tip) with the mayonnaise. Top each with a small dollop of the mayonnaise and a sprinkling of the toasted sesame seeds.