Preheat oven to 450°F. Place pizza crust on baking sheet. Spread spaghetti sauce over crust; sprinkle with 3/4 cup of the mozzarella cheese. Set aside. Mix water, soy sauce, cornstarch, ginger and garlic powder in small bowl until smooth. Set aside.
Heat oil in large nonstick skillet on medium-high heat. Add beef; stir fry 3 minutes or until no longer pink. Remove beef from skillet. Add broccoli to skillet; stir fry 3 minutes or until tender-crisp. Return beef to skillet. Stir soy sauce mixture. Add to skillet; stirring constantly, bring to boil on medium heat and boil 1 minute or until slightly thickened.
Spoon beef and broccoli stir-fry with slotted spoon evenly onto pizza crust. Sprinkle with remaining 3/4 cup cheese.
Bake 8 to 10 minutes or until cheese is melted. Sprinkle with sesame seed.