This is a classic salad to serve with a steak dinner.
In a small bowl, whisk together mayonnaise, chili sauce, milk, vinegar, relish, parsley, scallion, and 1/4 teaspoon each salt and pepper.
Place iceberg wedges on a platter or divide among 4 plates; drizzle with dressing, as desired. Serve immediately.
The dressing can be refrigerated in an airtight container for up to 2 weeks. Before serving, whisk to loosen.