Bring a large pot of water to a boil and cook the sweet potato noodles according to package directions, or until al dente. Drain, rinse under cold water, and set aside.
Slice and chop all vegetables, onions, garlic, and green onions so they’re ready to cook.
In a small bowl, whisk together soy sauce, sugar, sesame oil, and black pepper until the sugar dissolves.
Heat your Blackstone griddle (or a large skillet) to medium-high heat. Add 2–3 tablespoons of oil.
Sauté garlic and onions for about 2 minutes, until fragrant.
Add bell peppers and carrots, cooking another 2 minutes.
Toss in the spinach and cook just until wilted.
Move all vegetables to the side of the griddle.
On the other side of the griddle, add 1 tablespoon of oil. Cook the sliced beef with 2–3 tablespoons of the prepared sauce until fully cooked. Combine with the vegetables.
Add the cooked noodles and the remaining sauce. Toss everything together until well coated and heated through.
