Peel the potatoes and cut into equal sized pieces. Cook in boiling water with a pinch of salt for about approx. 20 minutes until tender. When the potatoes are almost cooked, heat the milk and finely chop the watercress. Drain the potatoes, add the hot milk and 75 grams of butter and mash until smooth. Stir the water cress through the mash. Season with pepper.
Heat the grill pan and grill the asparagus and leeks for approx. 5 minutes. Turn them regularly. Cook the peas in boiling water for about 3 minutes until just tender.
Slice 75 g of butter into cubes. Separate the eggs. Beat the egg yolks with a whisk in a saucepan over a low heat. Add the wine while beating until the sauce starts to resemble foam. Add the cubes of butter one by one and continue to whisk to create a bind the sauce. Season with salt and pepper.
Pat the cod fillets dry with kitchen paper and season with salt and pepper. Heat the rest of the butter oil in a non-stick frying pan. Fry the fish skin side down for about 5 minutes. Turn the fish and fry for another 2 minutes.
Arrange the grilled vegetables, peas and mashed potato over the plates and add the cod. Pour the sauce over the fish.
Tip: No mini leeks at your local green grocer? Use spring onion instead!
