Cauliflower-Potato Salad with Horseradish Dressing

Place potatoes in a 6-qt. pot with water to cover. Bring to a boil and cook for 6 minutes. Add cauliflower; cook until the vegetables are tender, about 4 minutes more. Drain, rinse with cold water to cool and drain again.

Combine yogurt, mayonnaise, mustard, horseradish, vinegar, salt and pepper in a very large bowl. Add the cooked vegetables, bell pepper and green onions and toss to coat. Top with freshly ground black pepper, if desired.