Place the quartered onions in a large slow cooker. Add the corned beef brisket, spice packet and beef broth.
Cover and cook for 5-6 hours on high or 8-10 hours on low until brisket is tender.
Remove brisket from the slow cooker and transfer to a plate or cutting board. Shred the brisket using a knife and fork. Add the shredded beef back into the slow cooker and mix together with the broth.
Serve corned beef in flour tortillas with sauerkraut, sour cream and chopped parsley.
Video
Notes
To freeze, cool the shredded beef to room temperature. Place in an airtight freezer bag, leaving about 2 inches of room at the top to allow for expansion, and freeze. It can be kept frozen for 4-6 months.To reheat, heat it up in medium pot on the stove or a large bowl in the microwave.