Cook the rice noodles according to package instructions. Drain and set aside.
In a bowl, toss the thinly sliced beef with cornstarch until evenly coated.
Heat 2 tablespoons of vegetable oil in a large skillet or wok over medium-high heat. Add the beef and cook for 2-3 minutes per side until browned and crispy. Remove from the pan and set aside.
In the same pan, add the remaining 1 tablespoon of oil. Stir-fry the red bell pepper, broccoli, and green onions for 3-4 minutes until slightly tender but still crisp.
Stir in the minced garlic and grated ginger, cooking for another 30 seconds until fragrant.
In a small bowl, whisk together all the ingredients for the sticky sauce. Pour the sauce into the pan, stirring well to coat the vegetables.
Return the cooked beef to the skillet, add the drained noodles, and toss everything together until fully coated in the sauce. Cook for 1-2 more minutes.
Remove from heat, garnish with extra green onions, and serve hot.