In a large bowl, season sliced beef with kosher salt, worcestershire sauce and 1 1/2 tsp. of cornstarch. Mix until thoroughly mixed to together.
In a small bowl, whisk together beef broth, soy sauce, sesame oil, crushed red pepper, ginger, sugar, minced garlic and onion powder. Set aside.
Heat a large skillet over medium heat. Add 1 tablespoon of the grapeseed oil and 1 tablespoon of butter. Once it is hot, add the beef. Cook beef in two batches. Cook beef, stiring constantly, until beef is almost cook thoroughly. Use a slotted spoon or spatula to transfer beef to a plate. Add another tablespoon of grapeseed oil, along with another tablespoon of butter. Cook second batch of beef. Transfer to plate with rest of beef.
In a small bowl or measuring cup, mix 1 1/2 teaspoon of cornstarch with 1/2 cup of water to make a cornstarch slurry.
Add prepared sauce to skillet, and bring to a simmer. Mix in cornstarch slurry and stir in broccoli and let simmer for 3 minutes, or broccoli's texture is to your liking Return beef to skillet and stir together with broccoli and sauce. Let simmer for an additional 2-3 minutes.
Serve immediately. Recommend to serve with rice.