For the asparagus mousse, peel the asparagus and cut into large pieces. Put on 0.5 liters of water and season with salt. Add 2 tablespoons of lemon juice and a pinch of sugar (if you don`t have a lemon on hand, just add an existing vinegar, e.g. white wine vinegar, etc.). Cook the asparagus for about 15 minutes.
Meanwhile soak the gelatine in cold water.
Thoroughly puree the cooked asparagus including the stock. Add 150 ml of cream and briefly bring to the boil again.
Melt the butter in a small saucepan. Stir in flour and stir thoroughly with a whisk (roux). Puree the roux in the asparagus mixture or stir thoroughly with a whisk. Squeeze out the soaked gelatine and also puree or stir thoroughly into the asparagus mixture. Season to taste with salt and pepper. Now place the entire asparagus mixture in the sink in cold water and stir until cool. Whip 250 ml cream until stiff and fold into the cooled asparagus mixture. Generously line a loaf pan with cling film (tip: lightly grease the loaf pan and then line it with cling film - the film will stick better to the shape). Pour in all of the asparagus mixture and put it in the refrigerator for at least 8 hours, or better overnight.
The final preparation the next day, as soon as the asparagus mousse has set, is the preparation of the cress mirror: Finely puree the crème fraiche with sour cream, watercress, salt, pepper and 1 tablespoon lemon juice. If necessary, stir in water or cream depending on the desired consistency (please do not puree any more with cream, otherwise it will become even more firm).
Arrange the plates as follows: Hard boil the eggs and quarter them. Wash cherry tomatoes and cut in half. Peel the cucumber if necessary and cut into sticks that are not too long - about a little longer than the length of the egg. Salt and pepper the eggs, tomatoes and cucumber
Arrange the cress mirror evenly on four plates, drizzle a few Lollo Rosso lettuce leaves with white wine vinegar and place in the middle of the plate on the cress mirror.
Lift the asparagus mousse out of the loaf pan with the help of the foil or turn it out of the loaf pan. Cut into slices that are not too narrow (6 slices are required for 4 people). Cut the slices or squares diagonally again so that small triangles are created. Place 3 triangles around the Lollo Rosso, evenly spaced from each other. Scatter eggs, tomatoes and cucumber across the entire plate.