Wash the meat and dab dry with kitchen paper. Heat 1 tablespoon of oil in a frying pan and fry the meat on all sides. Then fry over a low heat for a further 10 minutes while turning.
Season with salt and pepper, remove from the pan and allow to cool. In the meantime, mix vinegar, salt, pepper and sugar for the vinaigrette. Fold in the remaining oil. Peel the shallots and cut into fine rings.
Clean, wash and quarter the tomatoes. Clean, wash and pluck the lettuce into bite-sized pieces and drain well. Clean mushrooms, wash if necessary and cut into very thin slices. Mix lettuce, tomatoes, shallots and mushrooms.
Pour the vinaigrette over it and arrange on four plates. Slice the chicken thinly and also arrange it on the four plates. Sprinkle with pepper to taste and serve garnished with parsley.