Cook the glass noodles al dente according to package directions. Drain, rinse with cold water, and toss with a drizzle of sesame oil to prevent sticking.

Toss the sliced steak with 1 tablespoon soy sauce and black pepper. Let marinate for 5-30 minutes. Whisk together the sauce ingredients (1/4 cup soy sauce, maple syrup, and sesame oil) in a small bowl.

Heat 1 tablespoon olive oil in a large sauté pan or wok over high heat. Add the steak and cook for 4-5 minutes until browned and cooked through. Transfer to a plate and set aside.

Reduce heat to medium-high and add the remaining 1 tablespoon olive oil. Sauté the onion for 3 minutes, then add the mushrooms, bell pepper, carrot, and garlic. Cook for 4-5 minutes until tender-crisp. Stir in the spinach and cook 2 minutes until wilted.

Remove from heat. Add the cooked noodles, steak, and sauce to the pan. Toss everything together until well combined. Taste and adjust seasoning, then garnish with sesame seeds and sliced green onions.