For the green sauce, select the herbs, put a few stalks aside, wash them well and then, if possible, spin dry in a salad spinner.
Mix yogurt and mayonnaise in a bowl and season with salt, pepper, a pinch of sugar and vinegar or lemon juice.
Cut the chives into fine rolls and add to the dressing.
Chop the remaining herbs very finely with the food processor or a large, heavy kitchen knife. Also add to the sauce and mix well.
Boil the eggs hard, peel them and finely chop one egg and add to the sauce. Put the remaining eggs aside.
Wash the potatoes and cook them in plenty of salted water. Cut off a lid from the potatoes, scoop out slightly and flatten at the bottom. Season the green sauce again to taste, then pour a teaspoon into the potatoes. Eighth eggs and place on top of the sauce. Garnish with the herbs that were set aside.