In bowl, stir together half each of the cornstarch and soy sauce with the lemon juice; add beef and stir to coat. In separate bowl, stir together milk, remaining cornstarch and soy sauce and hot pepper sauce; set aside.
In wok or non-stick skillet, heat oil over high heat; stir-fry beef mixture and onion for 2 min or until browned. Add garlic, ginger and broccoli; stir-fry for 2 min.
Stir in milk mixture; cook, stirring often, for 4 min or until sauce is thickened and broccoli is tender-crisp.