Clean and quarter the white cabbage, remove the stalk and cut or slice the white cabbage into fine strips. The easiest way to do this is with a food processor. Peel the carrots and grate finely. Cut the onion into fine strips.
For the dressing:
Squeeze the lemon, mix the juice with mayonnaise, yogurt, milk and apple cider vinegar. Season the dressing with 1 teaspoon salt, pepper to taste and sugar. Fold in the white cabbage and carrots and mix well. Best to shake in a bowl with a lid. Chill the salad for at least 2 hours and let it steep.
Season again with salt and pepper before serving. Wash the parsley, shake dry and serve the salad garnished with parsley.