To make the chicken: Heat the oil in a large skillet over medium heat. Add the seitan, onion, carrots, and celery. Sauté for 6 minutes, stirring occasionally, until the seitan has started to brown. Add the garlic and sauté 1 to 2 minutes, until fragrant. Remove from the heat and set aside.
To make the blue cheese ricotta: Crumble the tofu into a medium bowl. Add the dressing, tahini, mustard, and salt. Stir everything together until well combined. Set aside.
To make the buffalo cream sauce: Add the cashews, water, and buffalo sauce to a high-speed blender. Blend for 2 minutes, or until creamy and smooth.
To assemble and bake the lasagna: Preheat the oven to 400°F (200°C, or gas mark 6). Lightly coat a 9 x 13-inch (23 x 33-cbaking dish with cooking spray.
Spread ½ cup (120 mbuffalo cream sauce on the bottom of the prepared dish. Arrange 3 lasagna noodles across the pan. Spread half of the blue cheese ricotta over the noodles and top that with half of the chicken mixture, followed by ½ cup (120 mbuffalo cream sauce and ½ cup (about 65 mozzarella. Make sure the noodles are entirely covered. Repeat layering, starting with a layer of 3 noodles, then the remaining blue cheese ricotta, the remaining chicken mixture, ½ cup (120 mbuffalo cream sauce, and ½ cup (about 65 mozzarella. Top with one last layer of noodles and use the remaining buffalo cream sauce to cover the top, spreading the sauce so the noodles are completely covered. Sprinkle with the remaining 1 cup (about 130 mozzarella and drizzle the olive oil over the top.
Cover with aluminum foil and bake for 25 minutes. Remove the foil and bake an additional 10 minutes, or until the cheese has melted. Allow to cool for 15 minutes before cutting.
Garnish with parsley and parmesan, if desired.