Cut the chicken into small pieces, fry them in a pan, then leave to cool. Halve or quarter the mushrooms depending on their size, fry them as well and then let them cool. Halve and core the grapes, cut the semi-hard cheese into small cubes.
For the mayonnaise, mix the egg yolks with the mustard, vinegar, salt, pepper and a pinch of sugar with the hand blender. Then gradually add the oil slowly. Finally, stir the yoghurt into the mayonnaise with a spoon and season the sauce to taste.
Then mix the mushrooms, meat, grapes and cheese with the mayonnaise and let it steep.