Start by making the dressing. Mix all the ingredients for the dressing together and season well.
For the Beetroot
Leave the skins on the beetroot and place them in a pot, cover with water and bring to the boil, then turn down to a simmer. Allow this to cook until the beetroot is tender. Remove from the water and allow them to cool slightly. Once they are cooled enough, use a cloth to remove the skins. Place them in a blender and bring them to a smooth puree.
To prepare the greens, separate them and remove any large stalks form them and keep them for the dish. At this time of the year the greens should be tender.
To cook the fish
Put a pan on medium to high heat. Season the fish with salt and pepper. Put a drop of rapeseed oil into the pan and lay the fish fillets in the pan, skin side down. Fry until the skin is golden and crisp, and the fillets are cooked two-thirds of the way through.
Turn the fish over and cook the flesh side for another 2 minutes or so. Once you feel the fish is almost cooked. Turn off the heat and allow the fish to rest. This time will give you enough time to cook the greens. Wash the greens and keep a little water on them. Heat a pan, if there are any stalks from the greens, add them to the pan first with a little water, and give them a minute or so. Then add the greens toss them in the pan for a minute or two until they have wilted. Season with some salt and pepper.
Place some greens in the centre of the plate, spread some beetroot around the plate, and place the fish on top. Drizzle some dressing over the fish.