Start with about 7 cups of unpeeled potatoes sliced into disks. Cook the sliced potatoes until they are tender then rinse and drain them. Put them in a bowl while they are still hot and cover them with about a half of a cup of Italian salad dressing. The heat helps the potatoes to absorb the flavor of dressing better.
Let them marinate in the refrigerator for a couple of hours and then lift them out of the dressing. In another bowl, blend together a half a cup of sour cream, a half of cup of mayonnaise, 2 teaspoons of horseradish (I prefer Ingellhoffer brand hot horseradish. It has a bite, but not painful.), 3 green onions that have been finely chopped (If you don't have green onions handy, finely chopped yellow or red onion (about 1/4 cup) works just fine.) along with 2 tablespoons of fresh dill (I use dried dill weed because I like a bit more of the taste.) and salt and pepper to taste.
Blend all of these ingredients together and then fold in the potatoes, refrigerate until ready to serve.