In a large heavy based pot, add ingredients for the stock. Pour over enough water to just cover the corned beef. Bring to the boil, skimming away any impurities that rise to the surface, then lower the heat and simmer, uncovered for 2 hours or until meat is lovely and tender. Remove the corned beef from the stock and set aside to cool.
Dice the corned beef and transfer it into a large mixing bowl. Add grated potato, red onion, spring onion, parsley and a good pinch of salt and pepper. Mix with your hands until well combined.
Heat a little oil in a frying pan over medium-high heat. Using a spatula, press the corned beef mixture into a flat cake, and cook until the mixture is browned and crusty on the bottom, about 10 minutes. Flip the cake, and continue cooking until the mixture is browned and crusty on other side, about 8 minutes.
Transfer to a plate, cut into wedges and serve with bacon and eggs.