1. Bring a large pot of water to boil. Cook soba noodles until tender, about 5 minutes, or as package label directs (spaghetti will take longer, about 10 minutes). Drain.
2. In a large bowl, whisk soy sauce, cornstarch, sugar, vinegar and broth. Add pork and toss to coat. Set aside to marinate for 10 minutes at room temperature.
3. Warm oil in a large nonstick wok or skillet over medium-high heat. Add pork and marinade; stir-fry until meat is no longer pink, about 3 minutes. Add cabbage and stir-fry until just wilted, about 2 minutes. Stir in carrot and snow peas; cook, stirring vigorously, until snow peas are slightly softened yet firm, about 2 minutes. Stir in noodles and toss to coat with sauce and warm through, about 1 minute. Season with salt and pepper. Divide mixture among 6 bowls, sprinkle with scallions and serve.