Cook the pasta in boiling salted water for about 9 minutes. Drain, rinse with cold water, drain and allow to cool. In the meantime, clean, wash and slice the celery.
Clean, wash and cut the salad into bite-sized pieces. Wash and clean the mushrooms and slice them into thin slices. Wash, quarter, seed and chop the pears. Sprinkle with the juice of 1/2 lemon.
For the sauce, crumble the gorgonzola, puree with sour cream, juice of 1 lemon and lemon peel. Season to taste with salt and pepper. Mix all salad ingredients with the sauce. Cut half a lemon into slices, arrange salad on plates and garnish with the lemon slices.