M&S Potato Topped Ocean Pie Frozen Succulent haddock in a creamy parsley sauce, topped with mashed potato and a Cheddar cheese crumb coating. Simply bake in the oven. Serves 1. Our M&S seafood products have been sourced from fisheries and fish farms in a way that minimises their ethical and environment impact, while guaranteeing you the highest quality, delicious seafood you’d expect from M&S.