Roast fish bones and trimmings in the oven till golden brown.

Add butter into a pot, saute chopped onions and leek till transculent. Add in the caramelized bones and trimmings and add water to cover the bones.

Add in mussels, 500 ml white wine, rosemary, dill and thyme.

Cook for 15 minutes, remove mussels and continue to simmer the sauce for another hour till it reduces to by 2/3.

Strain the concentrated sauce, and bring it back to a boil. Season with salt and pepper to your liking and pour the remaining wine in. Let it reduces by half, and start adding cold butter while stirring constantly until a shine forms on the sauce.

Season with salt and black pepper to your taste. Set aside sauce

In another pan, heat olive oil and cook the fish skin side down first. Each side cooks for 3 minutes.

Flip the fish and start adding cold butter, thyme and garlic. Start to baste the fish (spooning the melted butter with the herbs in it over the fish over and over again)

Remove and let the fish rest for 2-3 minutes.

Pour sauce, garnish with chopped carrots and radish. Plate the fish.