Peel and wash the potatoes. Clean broccoli and peel and wash carrots. Cut broccoli into florets. Chop the carrots if necessary
Cook the potatoes in salted water for about 20 minutes. Cover the carrots and cook in salted water for about 15 minutes. Cook broccoli for about 5 minutes
Wash the salmon, pat dry and sprinkle with lemon juice. Heat the oil in a pan. Fry the salmon for 3-4 minutes on each side. Season with salt and pepper
Peel and finely chop the onion. Heat 1 tbsp. butter. Sauté onion in it. Dust with flour. Add stock and cream while stirring, bring to the boil. Stir in mustard and simmer everything for about 5 minutes. Season to taste with salt and pepper
Drain the vegetables, melt 1-2 teaspoons of butter on top. Heat milk. Drain and mash the potatoes. Stir in the milk. Season with salt and nutmeg. Arrange everything (possibly sprinkle puree) and garnish with mint