Wash parsley, shake dry and pluck leaves from the stalks. Chop leaves finely. Clean, wash and slice the celery. Wash lemon, grate dry and finely grate half of the peel.
Mix lemon zest, yoghurt and parsley, except for a little bit for garnishing. Season to taste with salt and pepper, stir in celery.
Boil the eggs in boiling water for about 6 minutes, remove and quench. Peel and quarter the eggs. Spread the salmon on the slices of bread, put 2 quarters on each. Spread the sauce on top and garnish with the remaining parsley.