Chop the cauliflower into pieces and boil for about 15 minutes until tender.
While the cauliflower is boiling, chop the onion into pieces and fry gently until soft.
Add the cod to the pan and cook until it is done.
Pull the cod into pieces and add to a casserole dish with the onion and cauliflower.
In a pan melt the butter and add the flour. Gradually add the milk, stirring all the time, until the sauce thickens.
Grate the Wensleydale and apple cheese and add to the sauce. Pour over the cauliflower, cod and onion.
Grate the vintage cheddar and add to the top of the dish
Place under a grill until the cheese melts
Season with black pepper