Poach haddock in water to cover for about 10 minutes, drain well and flake fish. Combine with mashed potatoes, parsley and pepper, and roll into balls. Dip in beaten egg, then roll in breadcrumbs. Heat oil in a deep pan and deep-fry haddock balls until browned and crisp, about 10 minutes.
Serve hot as a snack, or as a light meal with chips and a salad.