Sort the leaves and tender stems of the watercress. Peel the onion and cut into strips. Quarter peppers, remove seeds and dice them.
Whisk the eggs with the cream, season with salt, pepper and some freshly grated nutmeg. Fold in watercress.
Heat 3 tablespoons of olive oil in a coated pan (24 cm Ø), sauté the onions and peppers for 2 minutes. Pour the egg watercress mixture over it. Cover the pan and let the sardines simmer on a mild heat for 10-12 minutes.
Meanwhile, for the dressing, chop the olives finely, dice the dried tomatoes finely. Coarsely chop parsley leaves. Whisk the remaining oil (4 tablespoons) with vinegar and 3 tablespoons water in a bowl.
Add dried tomatoes, olives and parsley. Season everything with salt, pepper and sugar.
Turn the sardines in the pan with the help of a lid, tear them into pieces with two tablespoons and cook for 2-3 minutes without a lid. Serve with the dressing.