1. Place the potatoes in a large pot with enough water to cover. Bring to a boil, and cook for about 10 minutes, or until tender. Drain, and place in a serving bowl.
2. Stir the onion, salt and pepper into the potatoes while they are still hot. This allows the potatoes to absorb the flavor. Allow to cool for about 20 minutes.
3. Add the mayonnaise, mustard and horseradish to the salad, and mix well. Gently stir in the eggs and dill pickles. Finish off with a generous grinding of black pepper on top. Chill for about 30 minutes before serving.

Directions

1. Bring a large pot of lightly salted water to a boil. Add the macaroni, and cook until tender, about 8 minutes. Rinse under cold water and drain.
2. In a large bowl, mix together the mayonnaise, vinegar, sugar, mustard, salt and pepper. Stir in the onion, celery, green pepper, carrot, pimentos and macaroni. Refrigerate for at least 4 hours before serving, but preferably overnight.

1. Preheat oven to 400 degrees F (200 degrees C). Butter a 1 quart casserole dish.
2. Layer 1/2 of the potatoes into bottom of the prepared casserole dish. Top with the onion slices, and add the remaining potatoes. Season with salt and pepper to taste.
3. In a medium-size saucepan, melt butter over medium heat. Mix in the flour and salt, and stir constantly with a whisk for one minute. Stir in milk. Cook until mixture has thickened. Stir in cheese all at once, and continue stirring until melted, about 30 to 60 seconds. Pour cheese over the potatoes, and cover the dish with aluminum foil.
4. Bake 1 1/2 hours in the preheated oven.