Cut the fish into chunks, removing any remaining bones.
Bring a large saucepan of water to the boil, add the tagliatelle and return to the boil. Cook
for 8-10 minutes, or until just tender.
Meanwhile, blend 125ml / 4 fl oz of the milk with the cornflour in a large, heat proof bowl.
Place the remaining milk in a saucepan with the shallots and bring to the boil. Pour the boiling
milk over the cornflour mixture, stirring constantly. Return the milk to the saucepan and return to
the boil, stirring constantly, until the sauce thickens.
Stir the fish into the sauce, reduce the heat to low and simmer gently for 5 minutes, or until
the fish is cooked. Stir in half of the chives.
Drain the tagliatelle and return to the saucepan, stir in the haddock sauce and season with
pepper. Serve immediately, garnished with the remaining chives.