Slice beef into bite size thin strips and place in bowl. Rub raw beef in seasoning blend of salt, black pepper, white pepper, garlic and onion powder, mustard powder, worchestire sauce and set aside
Make sauce
In a medium bowl, whisk together the beef consommé (or broth), soy sauce, oyster sauce, brown sugar, minced garlic, cornstarch, sesame oil, onion powder, and black pepper etc until the cornstarch is fully dissolved.
Pour this mixture over the sirloin steak in the slow cooker.
Cover with the lid and cook on LOW for 6-8 hours (or HIGH for 3-4 hours), until the beef is fork-tender and easily pulls apart.
During the last 30 minutes of cooking, add the broccoli florets to the slow cooker and stir them into the sauce.
Place the lid back on, increase the temperature to HIGH (if cooking on LOW), and continue cooking until the broccoli is bright green and tender-crisp.