Prepare the filling:
- While prepping the ingredients preheat the slow cooker
- Add half the onions and mushroom to the bottom of the slow cooker followed by the top round steak
- add the onion soup mix to both sides of the steak
- add the remaining onions and mushrooms on top then add the beef broth
- Cover and cook on low for 8 hours
- Remove about 1/4 cup of juice from the crock pot and add to a separate bowl with cornstarch. Whisk together and add back into the crock pot
- Turn the heat on high and cook without a lid for an additional 15-20 minutes stirring occasionally
- Enjoy!