In a large pot of boiling water, cook potatoes for 20 minutes or until tender but not mushy.
Drain and let cool slightly, peel.
With a potato masher, mash until smooth, do not use an electric mixer, blend in cream cheese and butter until melted.
Mix in onions, sour cream, parsley, marjoram, and salt and pepper to taste.
Transfer to 8 inch (2 L) baking dish, smooth top.
Sprinkle with crumbs, (Casserole can be prepared to this point, covered and refrigerated for up to 2 days or frozen for up to 1 week. Let thaw in refrigerator for 24 hours. Add 10 minutes to baking time.) Bake in 400 degree oven for about 20 minutes or until heated through and top is lightly golden.