Add the sour cream to a medium mixing bowl. Sprinkle in the Hidden Valley Original Ranch Seasoning Mix and stir until the seasoning is evenly distributed throughout the sour cream.
Stir in the mayonnaise, if using, for a slightly richer texture. Add the black pepper and chopped chives if desired. Mix until everything is smooth and well combined.
For a thicker dip, leave the mixture as it is. If you prefer a slightly thinner consistency, add the milk a teaspoon at a time, stirring after each addition until the dip reaches your desired texture.
Cover the bowl and refrigerate for at least 30 minutes. This resting time allows the herbs and seasonings to blend into the creamy base. For a more developed flavor, chill the dip for 1 to 2 hours.
Give the dip a quick stir before serving. Transfer it to a serving bowl and garnish with a few chopped chives, if desired. Serve cold with vegetables, chips, crackers, or your favorite snacks.