For the cauliflower purée, cut off all the florets quite small and fine, discarding the stalks.
Put the cauliflower in a pan and cover with the milk, cream, butter and salt and bring to a simmer.
When the cauliflower is tender, drain, retaining the cooking liquid. Put the cauliflower into a blender and pulse. Add a little of the cooking liquid and blend to a smooth purée. Season with salt and keep warm until ready to serve.
For the asparagus, peel away all of the woody leaves from around the spears, leaving the tip intact.
Heat a pan of salted water and mix in the butter to form an emulsion. Cook the asparagus until tender, about 2- 3 minutes.
For the cod à la polonaise, put the eggs in a saucepan and add enough water to cover the eggs by 1cm/½in. Bring to a boil then reduce the heat and simmer for seven minutes. When cooked, immediately cool the eggs under cold running water. Peel away the shell, then separate the whites from the yolks. Using a fine grater, grate both the yolks and whites separately.
Shallow fry the breadcrumbs in duck fat or olive oil until golden-brown. Drain and set aside.
In a mixing bowl, add the grated eggs, cornichons, shallot, parsley and chives, lemon zest and the fried capers. Season with salt and pepper and set aside.
Preheat the oven to 200C/400F/Gas 6.
Season the cod fillet with salt and pepper. Heat a little pomace olive oil in an ovenproof pan. Fry the cod on both sides until well coloured. Transfer to the oven to cook through - for a large piece of fish this will take about 4-5 minutes.
When the fish is cooked, season again with salt and pepper. Squeeze lemon juice over the top.
Brush the cod with Dijon mustard then pile the polonaise garnish on top of the fish.
To serve place the cauliflower purée on warm plates, put the cod on top and the cooked asparagus next to the cod. Sprinkle the fried breadcrumbs over the top and serve.