To make a Béchamel sauce, melt 50g of butter in a heavy-bottomed pan. Add the flour and allow to cook, stirring continuously for 10 minutes to make a roux. Warm the milk and slowly add to the roux. Mix continuously until smooth.
Cut two fennel bulbs in half. Blanch in boiling salted water until cooked. Remove from the water and dry. Pan fry until golden brown.
Soak the beans in cold water for 12 hours, then strain. Caramelise half a carrot, half an onion, half a celery stick, half a garlic bulb and a small piece of pancetta in a heavy-bottomed pot. Add in the soaked haricot beans and cover with 250ml of white wine. Reduce the wine until dry and then cover with the chicken stock. Keep the beans covered with stock until they are cooked. When cooked, strain the liquid and remove the vegetables and pancetta.
Place the fresh mussels into a hot pot. Add 175ml of white wine and cover immediately with a lid. Allow to cook for a few minutes until the mussel shells start to open. Remove from the heat and strain through a colander retaining the mussel stock. Discard any mussels that are still closed. Remove the mussels from the shells and place eight mussels aside, and a further eight mussels in their shells for later.
Thinly slice four shallots and slowly sweat down. Add the mussel stock and reduce until almost dry. Add 1 tablespoon of the Béchamel. Then add the whipping cream and the mussels. Bring to the boil. Blend the mixture together and pass through a fine sieve. Add the juice of quarter of a lemon and white pepper to taste. Dice the anchovy into ½cm cubes. Dice the remaining carrot, celery stick and fennel into 1cm cubes. Sweat the vegetables until they are almost cooked. Add the mussel sauce and the diced white anchovy. Take the eight mussels that were set aside and add to the pot along with the chiffonade of spinach and the cooked haricot beans to the pot.
Take the portioned monkfish and sear on all sides until golden. Place in an oven for approximately seven minutes at 180C/Gas Mark 4. Remove to rest for five minutes before serving.
Place two slices of white bread with crusts removed into a blender. Once the bread has reached a fine consistency remove and set aside for later. Place the fresh parsley and one clove of garlic into the blender and blitz. Lightly fry the garlic and parsley and allow to cool. Combine the bread, the soft butter and freshly grated Parmesan with the garlic and parsley mixture. Season to taste. For each dish take two clean mussel shells with cooked mussels inside. Top with the stuffing and bake for approximately five minutes at 170C/Gas Mark 3.
Spoon out the haricot bean and mussel mixture. Add two stuffed mussels to each plate and complete with monkfish and fried fennel. Garnish with finely chopped chilli.