Prepare the noodles. Boil 180g sweet potato noodles for 6–7 minutes until chewy. Rinse under cold water, drain, and toss lightly with 1 tsp sesame oil to prevent sticking.
Marinate the chicken. Mix 150g sliced chicken breast with 2 cloves minced garlic, 1 tsp soy sauce, and a pinch of ground black pepper. Let it sit for 10–15 minutes while you prep the vegetables.
Slice the vegetables. Cut 1 medium carrot, 1 bell pepper, and 1 medium yellow onion into thin strips. Drain and slice 100g shiitake mushrooms. Wash 100g spinach and set aside. Slice 2 stalks green onions for finishing.
Make the sauce. Combine 3 tbsp soy sauce, 1 tbsp honey (or sugar), 1 tsp mirin (optional), and salt & pepper to taste in a small bowl. Set aside.
Cook the chicken. Heat 1–2 tsp cooking oil in a pan over medium heat. Cook the marinated chicken for 3–4 minutes until lightly browned and cooked through. Remove and set aside.
Stir-fry the vegetables. Heat 1–2 tsp cooking oil in the same pan. Cook the onion for 1–2 minutes, then remove. Cook the carrot for 1–2 minutes and remove. Next, cook the bell pepper for 1–2 minutes and remove, followed by the mushrooms for 1–2 minutes. Finally, stir in the spinach just until it wilts lightly.
Combine noodles, chicken, and sauce. Return all the vegetables and the cooked chicken to the pan. Add the noodles and pour in the sauce. Toss everything together for 1–2 minutes until evenly coated and heated through.
Finish the dish. Turn off the heat. Drizzle 1 tbsp sesame oil, sprinkle 1 tsp toasted sesame seeds, and top with the sliced green onions. Toss lightly and serve warm.