Peel the onions and cut them into rings. Cut the pickles into slices. Wash, core, quarter and then slice apples. Cut the herrings into small pieces. When all the ingredients are cut into small pieces, place in a bowl.
Mix the crème légère, sour cream, horseradish and mustard to a sauce. Salt and pepper to taste. Then add the sauce to the ingredients. Mix everything well and let it steep in the refrigerator for at least 2 hours before you can eat it.