Mu Shu Seitan

Heat the oven to 400°F. Put 1 1/2 cups water in a small saucepan and bring it to a boil. Put the mushrooms in a small bowl, pour over enough boiling water to cover them by 1 inch, and let sit; reserve the rest of the boiling water. Thinly slice the seitan and put it in a medium bowl. Add the tamari, mirin, and sesame oil and toss to coat.

Rinse and trim the cabbage and carrots; peel the carrots. Shred the cabbage and grate the carrots either by hand or in a food processor. Rinse, trim, and thinly slice the celery. Peel the ginger and chop it with the garlic.

Put 5 teaspoons vegetable oil in a large skillet over medium heat. When it’s hot, add the ginger and garlic and cook until they’re fragrant, about 1 minute. Add the cabbage, carrots, celery, and 2 tablespoons of the mushroom soaking water to the pan. Cook, tossing and adding more mushroom water 1 tablespoon at a time as necessary to prevent sticking, until the celery and cabbage begin to soften, 5 to 7 minutes. Remove the mushrooms from the water and slice the caps thinly; reserve the water.

Whisk together the mustard powder, 2 tablespoons of the boiling water, and the remaining 1 teaspoon vegetable oil in a small bowl. Taste and adjust the seasoning with salt. Rinse, trim, and chop the scallions. Chop the prunes.

Wrap the tortillas in foil and put them in the oven until they’re warm, 5 to 10 minutes. Add the sliced mushrooms, seitan, and marinade to the skillet along with 1/4 cup of the reserved mushroom soaking water. Cook, stirring frequently until most of the liquid has evaporated, 8 to 10 minutes. Taste and adjust the seasoning. To serve, heap the mu shu on a platter and pass the tortillas, scallions, prunes, and hot mustard sauce on the side. To eat, spread a little mustard sauce on a tortilla, fill it with mu shu, sprinkle with scallions and prunes, and fold or roll to enclose the filling.