Mackerel with Mustard Sauce (Makreel met Mostersaus)

I've eaten a lot of smoked mackerels, bur never had a fresh peace in my hands. Until De Krat brought me one, or actually two fillets. Including a recipe, which I tried immediately as fish should be eaten as fresh as possible. What I particularly likes about the dish is the crispy skin and the nice solid texture of the fish.

Needed:

2 mackerel fillets with skin

1 red onion, chopped

Fresh Parsley

100 ml white wine 

1 bay leaf

2 el mustard

30 g butter, cold and chopped

Preheat the oven at 250ْ  C, season the mackerel with some salt and black pepper. Create, in the middle of a baking dish, a mound of the onion, bay leaf and parsley (keep a bit aside for the garnish). Put the fillets on top with the skin side up, pour the wine over and put in the oven. Cook for 7-10 minutes, depending on the thickness of the fillets. Put the fillets aside on a warm serving dish as soon as they're done, cover with some aluminum foil to keep warm.
Strain the cooking liquid from the baking dish in a small saucepan and boil for a couple of minutes to concentrate. Add the mustard and stir, the whisk the butter through and let it simmer for about 3 minutes. Pour the sauce over the fish and garnish with same parsley.
Very nice with some skin cooked potatoes and a green salad. Very light, the fish is oily enough by itself.