Add beef, stir fry sauce, brown sugar, water, and ginger in a slow cooker. Stir to combine.
Cover, and cook on low 5 to 7 hours or high 2 to 3 hours or until beef is fork tender.
Combine cornstarch with 3 tablespoons water and whisk the slurry into beef mixture. Add broccoli to the slow cooker and cover.
Cook 15-25 minutes or until broccoli is tender-crisp and sauce is thickened.
Serve over rice or noodles.
Notes
Different brands of stir-fry sauce may be saltier. Add additional water if needed (You may need to add more cornstarch slurry at the end of cooking to thicken).
Freeze beef for 30-45 minutes to make slicing easier!
Be sure meat and broccoli are bite-sized for even cooking.
Prep and refrigerate meat and broccoli ahead of time until ready to use.
Leftovers will keep in an airtight container in the refrigerator for 4 days and in the freezer for 4 months.