1/4 cup finely chopped celery, divided
1/4 cup finely chopped green onions, divided
1/4 cup finely chopped parsley, divided
2 tablespoons canned and drained pimientos
3 tablespoons Dijon mustard
2 tablespoons red-wine vinegar
1 tablespoon prepared horseradish (not creamed)
1/2 cup mayonnaise
1/2 teaspoon paprika
1/8 teaspoon Worcestershire sauce
1/4 teaspoon salt
Place 2 tablespoons each of the chopped celery, green onion and parsley in a blender or food processor, along with the drained pimientos, mustard, vinegar and horseradish. Blend to a paste, then scrape out mixture and whisk into the mayonnaise, along with reserved celery, green onions, parsley and the paprika, Worcestershire sauce and salt.
Refrigerate for at least 1 hour so flavors develop. Adjust seasoning before serving. Sauce will keep for 3 to 4 weeks or longer (refrigerate).
Makes about 1 1/4 cups.