Bring large pot of water to a boil, add salt. Add soba noodles and cook according to package directions. Drain and set aside.
In a large cast iron skillet, heat oil over medium-high heat. Add tofu, season with coriander and salt and cook until browned on all sides. Remove from pan and set aside on a paper towel lined plate.
To the same skillet, add more oil if necessary, and sauté onions, mushrooms, carrots, broccoli until the veggies soften. Add ginger and garlic, let cook until fragrant, about 30 seconds.
Add soba noodles, soy sauce, chili-garlic sauce, hoisin sauce and bean sprouts and let cook for a few minutes, stirring until all noodles are coated in the sauce. Adjust seasoning as required. Serve immediately, garnished with scallions.