Bring a pan of water to the boil and cook the pasta according to the pack instructions.
Meanwhile, heat the butter in a saucepan, then add the shallot and cook for 5 mins or until softened. Add the frozen peas, fish, crème fraîche and 50ml water. Crumble in the stock cube. Cook for 3-4 mins until cooked through, stir in the chives and some black pepper. Then stir through to coat the pasta. Serve in bowls.