MaagNificent Mashed Potatoes

4-5 large Idaho potatoes#189; stick butter4 ounces cream cheese1 cup sour cream#188; cup prepared French onion dip3 cloves garlic, minced2 teaspoons prepared horseradish1 tablespoon Dijon mustard2 teaspoons Lawry's seasoned salt#188; teaspoon garlic salt2 cups shredded parmesan and Romano, dividedPeel and quarter potatoes. Boil for 25 minutes until easily pierced with fork. Drain and place in a large bowl.Add butter and cream cheese to potatoes and blend with hand mixer or potato masher.Heat oven to 350 degrees.In separate bowl combine sour cream, onion dip, garlic, horseradish, mustard, seasoned salt, garlic salt and 13/4 cups cheese. Fold in potatoes until well combined. Turn mixture into a 11/2- to 2-quart casserole. Top with remaining cheese.Bake, uncovered, 35-45 minutes or until heated through and browned.Serves eight.