In a large mixing bowl, combine the vital wheat gluten with the nutritional yeast. Add the 3/4 cup of water and the soy sauce. Knead until it forms a stiff dough, 2-3 minutes. Transfer to a cutting board and shape the dough into a flat log about 8 inches long and 4 inches wide. Set aside.

Combine the vegetable broth, garlic and 1/4 cup sliced ginger in a large pot and bring to a boil. Lower the heat to a very gentle simmer, and submerge the seitan in the broth. Simmer for 30 minutes, partially covered to allow steam to escape. Leave the seitan to cool completely in the broth.

In a wide, shallow bowl, whisk together the hoisin, mirin, remaining 3 tablespoons of water, Sriracha, teaspoon of minced ginger and sesame oil. Set aside.

When the seitan has cooled, remove from broth. Carefully slice off 16 slices about 1/8-inch thick (you’ll have extra seitan). Transfer the slices to the bowl of marinade, and marinate for 1 hour, flipping occasionally. After 1 hour, use a wooden spoon to push the seitan to one side of the bowl. Add the scallions to the marinade, keeping them separate from the seitan. 

Place some toothpicks in a small bowl of water to soak.

Assemble the rolls. Place 1 slice of seitan on a plate. Arrange 4-5 scallions on the seitan, and roll the seitan up, with the ends of the scallions poking out on both sides. Use a toothpick to secure the rolls and complete with the remaining seitan and scallions.

Heat a grill to medium. Brush the grate with oil, then set the rolls on the grill and cook 2-3 minutes per side, flipping once, until grill marks appear. Transfer to a serving dish as they cook. Serve sprinkled with sesame seeds.