In a medium bowl, whisk together the yogurt (or mayonnaise) with sour cream, dill, parsley, garlic powder, onion powder, basil, and salt and pepper until well combined.
Slowly whisk in the milk and lemon juice until well incorporated.
Place the dressing in an airtight container and refrigerate for at least 30 minutes before using, to allow the flavors time to develop.
After 30 minutes serve as desired or store in the refrigerator for up to 7 days. Shake before each use.
Notes
In place of the dried spices, feel free to use 2 teaspoons of dried Ranch Seasoning. Buttermilk/Milk: Use any fat percentage of milk or buttermilk. Yogurt: Using yogurt in place of mayonnaise will lower the fat of the dressing and make it egg-free. Be sure to use PLAIN Greek yogurt, not flavored yogurt or regular plain yogurt. Sour Cream: Use regular or reduced-fat, not fat-free sour cream for best results.