This bit is optional but it makes all the difference. Put the butter into a pot and melt slowly, The whey will separate from the butter. Let it go to a light golden brown. Skim off the bubbles and put aside ready to use.
I like to cut off the fins and the sharp fins at the head. Put 3 slits in the thickest part of the fish on both sides ( see picture) Dry it with kitchen paper and brush with a little of the butter and salt and pepper inside and out.
Heat a frypan till very hot add a little butter and put the fish into the pan. Leave on high for several minutes until the pan starts to smoke, then carefully turn the fish over. ( see picture).
Put the fish into the oven in the frypan or transfer to a baking try. The fish will take approximately 15 minutes in the oven
Open the oven and test the fish. It will look opac and a little bit of juice will be sitting in the slits near the head ( picture)
Put the fish some where warm while you make the sauce
Put the frypan back on high add a teaspoon of the butter and the asparagus spears. ( add garlic and chilli, optional). Let them blister. Turn them once then add the capers, lemon and the rest of the butter. Taste the sauce for seasoning and add salt .
Add the parsley and mint stir and put the Asparagus onto a plate big enough to hold the fish. Put the fish onto the plate and pour over the sauce. Sprinkle with nuts and extra parsley and mint