Blue Cheese Dressing

Name: Blue Cheese Dressing
Ingredients: 6 ounces blue cheese, coarsely crumbled; 3¾ teaspoons horseradish; Juice of 1 lemon; 2 tablespoons white wine vinegar; 2¼ teaspoons garlic powder; ½ teaspoon dry mustard; 1 1/3 teaspoons freshly ground pepper; 4 cups mayonnaise; ½ cup buttermilk; ¼ cup (or less) water