A very simple recipe: just coat the fish in seasoned flour and fry on both sides until cooked, about 10 minutes total time per 1 inch thickness of fish.
(Apologies for the non-metric measure, but despite being a scientist, I'm old-school and still think in Imperial measures! And this was a guide to cooking fish
I learned a very long time ago!) Meanwhile, make a parsley sauce by melting a Tbs butter and adding a Tbs plain flour. Stir over a medium heat for 2-3 minutes,
to cook the flour, then add 300 ml whole milk, stirring all the time and heating gently, until you have a smooth thick white sauce. Stir in plenty of chopped parsley,
season with salt and freshly-ground black pepper, and serve over the cod with new potatoes and a green veg.