In a medium bowl, whisk together beef broth, soy sauce, oyster sauce, brown sugar, sesame oil and garlic.
Place beef into a 6-qt slow cooker. Add sauce mixture and gently toss to combine. Cover and cook on low heat for 90 minutes.
In a small bowl, whisk together 1/4 cup water and cornstarch.
Stir in cornstarch mixture and broccoli into the slow cooker. Cover and cook on high heat for an additional 30 minutes.
Serve immediately.
Notes
Use chuck roast. Chuck roast is most preferred for a slow cooker recipe like this one as the meat breaks down perfectly during the longer cook time, yielding tender, melt-in-your-mouth beef. Flank steak can also be used but can be tough and dry if cooked for too long.
Always slice across the grain. Slicing across the grain (slicing perpendicular to the long parallel muscle fibers) shortens the muscle fibers, yielding a more tender bite.
Use reduced sodium soy sauce. Reduced sodium has less sodium and less salt without compromising flavor.
Increase the cook time as needed. For more of a "pulled-pork" texture, increase the cook time to 3-4 hours.
Add the broccoli at the very end. To avoid soft, mushy broccoli, stir in the broccoli during the last 30 minutes to maintain its crisp-tender texture. If you prefer more crisp broccoli, add it during the last 15 minutes of cook time.
Add more veggies. This slow cooker beef and broccoli recipe is very flexible and forgiving. Add in carrots, bell peppers, snow peas or baby corn along with the broccoli during the last 30 minutes of cook time for a more heartier, well-rounded meal, ideal for picky eaters!
Make a cornstarch slurry. Adding cornstarch directly into the slow cooker can cause lumps. Always use a mixture of cornstarch and cold liquid (aka cornstarch slurry) to thicken the sauce, yielding a smoother, gravy-like consistency.
Serve with your favorite grains. White rice, brown rice, cauliflower rice, quinoa or farro are all great options.
Freeze leftovers. Beef and broccoli is incredibly freezer-friendly, keeping in the freezer for at least 2 months. Portion into plastic freezer bags in individual servings, thawing overnight in the fridge and reheating over low heat, stirring occasionally, until heated through.