Combine beef strips with 1.5 tablespoons sesame seeds in small bowl. Toss to coat well. Cut florets off broccoli stalk. Peel stalk and thinly slice crosswise. Combine broccoli florets and stalk with yellow pepper in medium bowl. Stir broth, soy sauce, ginger, garlic, cornstarch and crushed red pepper in another small bowl until cornstarch dissolves.
Heat 1.5 tablespoons oil in wok or heavy large skillet over high heat. Add beef and stir-fry until brown, about 2 minutes. Using slotted spoon, transfer beef to plate. Heat remaining 1.5 tablespoons oil in wok. Add broccoli and peppers and cover wok. Cook until vegetables are just tender, stirring occasionally, about 2 minutes. Stir broth mixture and add to wok. Add beef and any accumulated juices from plate. Simmer until sauce thickens, stirring occasionally, about 1 minute. Transfer beef mixture to platter. Sprinkle with toasted sesame seeds if desired.