Step-by-step preparation:

Preparing the greens: Rinse the watercress thoroughly with cold water. Be sure to dry it with paper towels so that excess moisture does not make the sauce runny. Finely chop the greens.

Preparing the savory cream: If using cream, beat it until thick. Add lemon juice, mustard, salt, white pepper and sugar. Mix thoroughly until smooth. Pour the chopped watercress into the mixture and mix again carefully.

Forming the rolls: Spread thin slices of salmon on a work surface. Grease each piece with the resulting creamy mixture. Carefully wrap the fish in tight rolls.

Cooling: Place the rolls on a plate, cover tightly with cling film (to prevent the fish from getting soggy and absorbing extraneous odours) and refrigerate for 30–60 minutes. This will allow the filling to set and the flavours to meld.

Serving: Arrange fresh lettuce leaves on a large plate, then top with the cooled rolls. Serve with warm, crispy toast.

Enjoy!