Remove the skin from the smoked haddock and cut into bite-sized pieces.
Trim and thinly slice or shred the fennel.
Melt the butter in a pan and add the fennel, cook for 5 minutes to soften.
Stir in the flour then gradually add the milk, stirring until you have a smooth sauce. Remove from the heat and stir in the fish, seasoning and add bay leaf.
Spoon into a 1.1 litre ovenproof pie dish and set aside whilst preparing the topping.
Set oven to 200C/400F/Gas Mark 6.
Bring a pan of lightly salted water to the boil, cut the potato into small chunks and slice the carrots. Cook until tender then drain and mash until smooth.
Stir in half of the cheese. Whip the egg white until stiff and fold into the potato mixture.
Spoon or pipe over the fish mixture and sprinkle with remaining grated cheese.
Bake for 30 to 35 minutes, until topping is golden and bubbling.
