Clean and wash the celery, put some celery green aside. Cut the stalks diagonally into thin slices. Wash, halve or quarter the grapes and remove the seeds. Cut apple into eighths, remove seeds and cut into pieces. Coarsely chop walnuts
Mix celery, grapes, apple and half of the walnuts. Mix sour cream and lemon juice, season with sugar
Cut the avocados in half, remove the stones. Fill the avocados with the celery salad. Spread sour cream over them, sprinkle with remaining nuts. Garnish with celery green and orange
Drink: cool white wine or wine spritzer