Take a recipe for marios.......
or another..........
basic ingredients, apart from Bish's spice mix, obtainable from the Deli in the Digey, St Ives.......
fill a baking tray with the beer and malt or cider vinegar, sliced onions, bay leaves, salt and pepper and a few teapsoons of Bish's spice mix.......
this will give the fish a rich, golden colour when they are done.......
pop in the fish and arrange the bay leaves.......
almost cover the fish with the brew......
tightly wrap the whole lot with foil.......
and pop in the oven overnight - even better in the bottom oven of an Aga - either way the temp needs to be around 110ยบ.