Pour a pint of milk into a pan and add a bay leaf. Gently warm the milk up being careful not to boil it, you want to allow the aromatics from the bay leaf to infuse with the milk. Once warmed, add the diced fish to the milk. Cook it all gently together for 5-6 minutes, then drain off the milk into a jug and put the fish in a bowl.
In a seperate saucepan melt the butter and add a few tablespoons of flour, stir it in well then gradually pour on the milk whilst stirring until you get a smooth creamy sauce. Flake up your fish then stir into the sauce, here you could add a handful of prawns too if you like and then season with salt and pepper.
Put the fish and sauce into an oven proof dish, top with really buttery mash and a sprinkling of grated cheese then place into the oven for 10 minutes, lovely.