1. Heat a large frying pan over medium-high heat. Cook the beef fry, stirring occasionally until the fat renders and the beef is crisped, about three to four minutes. Remove from heat.
2. Using a slotted spoon, transfer the beef fry to a paper towel and set aside. Do not discard the oil in the pan.
3. Combine flour, salt, and pepper in a ziploc bag. Add the beef cubes and shake to completely coat each piece in the flour mixture.
4. Prepare a four to six quart slow cooker.
5. Turn the heat under the frying pan to medium-high and sear the beef cubes in batches until they’re brown on all sides. Transfer the browned beef cubes to the slow cooker and continue until all the cubes are browned, adding additional oil as necessary. Spread the mushrooms and onions over the browned beef cubes.
6. Combine all remaining ingredients and pour over the beef and vegetables. Cover and cook on high for four to five hours or on low for eight to nine hours.
7. Stir in the beef fry pieces and cook uncovered for the last ten minutes.