(Nutrition information is calculated using an ingredient database and should be considered an estimate.)
Preheat the oven to 200C/180C fan/gas 6.
Place the potatoes in a pan of cold water, bring to the boil and simmer for 25mins until soft. Drain, steam dry for 2mins then return to the pan and mash with 80ml Elmlea Single and 20g Flora Buttery until smooth. Season to taste with sea salt and black pepper.
Meanwhile, place the fish in a saucepan, cover with the milk, heat to a gentle simmer for 5-8mins until the fish starts to flake. Drain the milk into a jug and set aside.
Melt the remaining 30g Flora Buttery in a saucepan with the leek, cover and sweat for 10mins until soft. Add the flour, stir to combine and cook for 2mins until it resembles a sandy consistency. Gradually add the fish poaching milk and remaining Elmlea Single, stirring between each addition, until you have a smooth sauce. Mix through the nutmeg, parsley, chives, peas and fish. Season to taste with sea salt and black pepper.
Tip into an ovenproof dish and top with the mashed potato. Bake in the oven for 20-25mins until golden and bubbling. Serve sprinkled with a few extra chives.
Freeze before baking for a get ahead weeknight meal. Defrost fully before baking to piping hot.