In slow-cooker, arrange beef strips; pour beef broth and oyster sauce over the beef.
Cover and cook on LOW for 6 to 8 hours or on HIGH for 3 to 4 hours or until beef is very tender.
If using fresh broccoli, place broccoli in microwave-safe bowl with 1/4 cup water. Microwave 4 to 5 minutes, until broccoli is tender. If using frozen broccoli, follow cooking directions on packaging.
In a cup, combine cornstarch and 2 tablespoons cooking liquid; stir until smooth.
Add to slow-cooker and stir well to combine. Drain the broccoli and stir into the slow-cooker. Cook uncovered on HIGH for about 15 minutes or until sauce is thickened. Serve over hot, cooked rice and garnish with sesame seeds.
Notes
*I had never purchased oyster sauce before making this, but I found it on the Asian aisle at my local grocery store, right by the teriyaki sauces. It was only about $2 and has such an amazing taste that totally makes this dish! I don't know what else you could use as a substitute . . . I highly recommend just trying it.