Scrub the potatoes and cook in a pan of boiling salted water for 15 minutes, then drain and steam dry.
Tip the potatoes into a large roasting tray, toss with a pinch of sea salt and black pepper and 2 tablespoons of olive oil, then roast for 15 minutes.
Meanwhile, trim the spring onions and asparagus, and finely chop the parsley, stalks and all.
When the time’s up, remove the potatoes from the oven, squash them gently with a potato masher, then push to one side. Place the spring onions and asparagus on the bottom of the tray, arrange the potatoes on top, then return to the oven for a further 15 minutes, or until the potatoes are golden and cooked through.
Finely grate the lemon zest into a small bowl, squeeze in half the juice, then add the chopped parsley. Stir through the cottage cheese, creamed horseradish and 1 tablespoon of extra virgin olive oil, then season to taste.
Toss the watercress in a squeeze of lemon juice and 1 tablespoon of extra virgin olive oil.
Pile the potatoes and veg onto a platter, spoon over a good dollop of creamy dressing, then arrange slices of smoked salmon and pinches of dressed watercress nicely on top.
