Poke small holes in the potatoes with a fork or knife. Bake the potatoes for 50 minutes - 1 hour, until crispy on the outside and soft on the inside. Remove from the oven and allow to cool.
Lower the temperature to 200°C/Gas 6.
Heat the butter in a frying pan over a medium heat. Once melted, add the leek and fry until soft, stirring occasionally.
Add the fried leek to a bowl together with the anchovies, seafood mix, crème fraiche, parsley and chives and stir to combine.
Cut the potatoes in half and scoop the flesh into the bowl with the seafood mix, leaving about 5 mm against the skin. Add the cheddar and stir to combine.
Fill each potato skin with the seafood filling and place on a baking tray – or use a bun tin.
Sprinkle extra cheddar over the potatoes and bake for 20-30 minutes until the cheese is gratinated.
