The day before: make the vinaigrette. Put the oregano or marjoram, a pinch of salt and garlic in a food processor and make a paste. Add the lemon juice and mix until smooth. Incorporate the olive oil and season – it can be strong and a bit salty. Cover and refrigerate.
Two hours before serving: bring a pot of salted water to a boil, add the asparagus and cook for 3 minutes. Drain and let cool under cold running water. Cover and refrigerate.
Put the beetroot in a large bowl and mix with two-thirds of the vinaigrette. Add the lemon zest and chives, cover and keep at a cool room temperature with the remaining vinaigrette.
To serve, add the watercress to the beetroot and tear in the basil. Mix with the asparagus and season with freshly ground black pepper. Taste before adding salt, as the cheese is salty. Mix very gently so as not to color everything pink, then put in a serving dish. Crumble the cheese on top and pour over the remaining vinaigrette.