Cook the udon noodles according to the package instructions, usually boiling them for about 8-10 minutes. Once cooked, drain and rinse under cold water to prevent them from sticking together. Set aside.

In a small bowl, whisk together the soy sauce, mirin, sake, sugar, grated ginger, and minced garlic until well combined. Set aside.

In a non-stick skillet, heat 1 tablespoon of vegetable oil over medium-high heat. Add the tofu cubes and cook until golden and crispy on all sides. Remove from the skillet and set aside.

In the same skillet, add the remaining tablespoon of vegetable oil. Add the sliced onions and cook for 2-3 minutes, or until they start to soften.

Add the carrots, bell pepper, and mushrooms to the skillet. Stir-fry for about 5-7 minutes, or until the vegetables are tender yet crisp.

Add the cooked udon noodles and tofu to the skillet with the vegetables. Pour the sauce over the top and toss everything together to combine well and heat through.

Stir in the bean sprouts and cook for an additional 2-3 minutes.

Transfer the Yaki Udon to serving plates. Garnish with sliced spring onions and a sprinkle of sesame seeds, if desired.

Serve hot and enjoy your homemade vegan Yaki Udon!