I follow this recipe, Eth.
400g Waitrose Frozen Fish Pie Mix
400g diced potatoes
1 tbsp olive oil
1 medium hard boiled egg, chopped
75g frozen peas, blanched
300g half fat crème fraîche
50g grated Parmigiano Reggiano
1 tbsp chopped parsley
20g fresh breadcrumbs
Preheat the oven to 190°C, gas mark 5.
Boil the potatoes in salted water until just soft. Drain and place back in the pan, lightly crush with a fork and drizzle with oil.
Place the fish pie mix in a frying pan with a little water and poach for 4-5 minutes until just cooked. Drain and season. Place in an ovenproof dish and add the chopped egg and peas.
Mix the crème fraîche with most of the Parmigiano Reggiano and parsley then season with cracked black pepper. Spoon the mixture over the fish. Spoon the potatoes on top and sprinkle with breadcrumbs and the remaining Parmigiano Reggiano. Bake for 25 minutes until golden.