In a pan, place cod with milk and thyme. Bring to the boil then cover and simmer for around 5 minutes or until the fish is cooked.
Meanwhile, in another saucepan, melt the butter and cook the leek till soft.
Drain the milk from the cod and add it to the leek mixture. Set the cod aside. Add the flour and stir in the milk gradually to make a paste. Add the cheese, bring to the boil and keep stirring for about 3 minutes or until the sauce thickens and the cheese has melted.
Mash the fish, carefully checking for any bones and mix with fish sauce. Add one tablespoon of water if too thick. If you want to reserve a few spoonfuls of sauce to use as a topping, pick out leek pieces if serving to a young baby.
Increase the ingredients according to your family’s size, skip the step 4 (except for the baby, of course) and serve this as a family meal.
This recipe will also work with haddock or other soft white fish.