Combine 2 tablespoons cornstarch with the salt. Add beef and toss to coat.
Heat oil in a wok or skillet over medium-high heat and add beef. Stir-fry about 4 minutes until lightly browned and cooked through. Transfer to bowl with slotted spoon and keep warm.
Add 1/2 cup broth to the pan and stir to loosen any bits of food on bottom. Add broccoli, cover and cook. Toss occasionally and sprinkle with water if necessary until broccoli is crisp-tender (about 3 minutes).
Add ginger, garlic and red pepper flakes and stir-fry for about 1 minute; until fragrant.
Stir together soy sauce, 1/2 cup broth, 1/2 tablespoon cornstarch and water in a cup until blended and then stir into pan.
Reduce heat to medium-low and bring to a simmer. Simmer about 1 minute until slightly thickened.