Toss steak and cornstarch together.
Heat oil in a large non stick, high sided, skillet over high heat. Add steak to pan and season with salt and pepper. Brown beef, about 5 minutes. Remove steak from pan and set aside.
While steak is cooking prepare peanut sauce by stirring together peanut butter, sriracha, garlic, soy sauce, sugar, rice vinegar and water until smooth. Set aside.
Add broth to pan and bring to a boil. Add egg noodles and cook just until tender. During last couple of minutes of cooking, toss in the broccoli. Stir in peanut sauce and return steak back to pan. Mix well to combine and coat evenly. Simmer 2-3 more minutes.
Serve topped with crushed peanuts and green onions.