Soak stockfish three days in cold water in cold place (I would suggest somewhere outside because it stinks, but be careful not to freeze it).
When softens, remove skin and bones and cut it into 5 to 10 cm pieces.
Peal potato and cut it into round pieces like for chips but thicker (0,5 cm).
Put potato into cold water, salt it a bit and cook just until boils, cut the heat and leave potato in the water (you will use that water later).
During this, cut garlic into small pieces and put it into pot with olive oil. Fry garlic just for 10 seconds and add stockfish. Stir everything with wooden ladle to cover stockfish with olive oil. Add wine and cook until alcohol evaporates (3-5-minutes).
Add potato, parsley, bay leaf, peppercorn and maybe salt (fish is very salty). Add some water from potato pot just to cover everything.
Cook not more than 15 minutes, otherwise stockfish will become like rubber.