To make the sauce: Place the soy sauce and mirin in a small saucepan. Slowly heat (do not boil). Add the sugar and stir to dissolve. Cool and reserve.
To make the noodles: In a sauté pan, heat the oil, ginger and garlic. Sauté until the garlic begins to soften. Add the mushrooms, broccoli and carrots. Cook on medium heat for 1 minute. Add the snap peas, tomatoes, soy-mirin base and vegetable or chicken stock.
Once warm, add the tofu and soba noodles. Heat through, add the scallions and place in a pot. Cover and serve.