Peel asparagus and cut stem. Bring water, white wine, sugar, salt and butter to a boil in a flat pot. Add the peeled asparagus. Cover with a cloth and cook al dente (approximately 10 minutes depending on the thickness). Remove asparagus, place on cold tray and refrigerate. Reserve broth.
Bring reserved broth to a boil, and add lemon peel. Remove from heat and allow water to infuse with lemon for 30 minutes. Strain broth, which will serve as a base for the vichyssoise. Blend broth, cream, butter and potatoes until a very fine consistency. Add salt to taste.
To prepare gnocchi, whisk and strain egg yolks. Put in a bowl, stir it until 130ºF (55ºC ), remove and chill with ice. Pour mix into a pastry bag for 24 hours and freeze. Then, chill pastry bag in the refrigerator for another 24 hours (or longer, if necessary, until defrosted). Cut the pastry bag, and pipe small gnocchi, reserving them in sunflower oil.
Once ready to serve, ladle ¼ of vichyssoise into a shallow bowl and garnish with asparagus, truffles, oil, croutons, flower petals and gnocchi. (Can be served either warm or hot.)