In a high container put cress, mayonnaise and yoghurt, season to taste with herb salt and pepper, then blend using a blender until homogeneous. Remove casing from the sausages, slice them and put on a pan with a few drops of rapeseed oil. Fry for 5 minutes, stirring occasionally, until sausage slices turn slightly golden brown. Put on a plate lined with a paper towel and set aside to cool. Put mange tout into boiling water, add some sugar and salt, then boil on a medium heat for 4 minutes. Drain and leave to cool.
Peel the mango and cut it into pieces. Remove the core form the pepper and cut it into pieces. Remove pistachios from shells and chop coarsely. On a platter put alternately the lettuce mix sprinkled with oil, mango, pepper and sausage slices. Pour sauce and finally sprinkle with pistachios and mange tout.