Lemongrass Tofu Banh Mi

Bread and Vietnamese filling-carrots and radishes, coriander, mayonnaise and cucumber-are traditional for this vegetarian version of the classic Vietnamese sandwich. Prepare the mayonnaise mixture and toast the bread while the tofu and vegetable mixture are marinated.
Cut the tofu crosswise into 6 2/3-inch thick slices. Spread the tofu on several layers of paper towels. Cover with extra paper towels; top with a cast-iron skillet or other heavy skillet. Let stand for 15 minutes. Remove the tofu from the paper towels.Combine 2 tablespoons of lemongrass, 2 tablespoons of water, soy sauce, and 1 teaspoon of sesame oil in a 13-inch x 9-inch glass or ceramic baking dish. Arrange the tofu slices in a single layer in the soy mixture, turning to coat. Let stand for 15 minutes.Combine the vinegar and the following 3 ingredients (with added salt) in a medium bowl, stirring until the sugar and salt are dissolved. Add carrots and radishes; mix well. Let stand for 30 minutes, stirring occasionally. Drain; add cilantro.Combine the remaining 1 teaspoon of sesame oil, mayonnaise and sriracha in a small bowl, stirring with a whisk. Slice the bread horizontally. Spread the mayonnaise mixture evenly over the cut sides of the bread.Preheat a large nonstick skillet over medium-high heat. Brush the mold with cooking spray. Remove the tofu from the marinade and drain the marinade. Dry the tofu slices with paper towels. Place the tofu slices in the pan and cook for 4 minutes on each side, or until crisp and golden. Place the tofu slices on the bottom half of the bread; top with the carrot mixture and cucumber slices. Cut the loaf crosswise into 6 equal pieces.