Heat oil over medium heat. Place one sprig's worth of curry leaves at a time in a skimmer or strainer ladle and fry the leaves until crisp. Keep the leaves in the oil for only a second or two at a time. The leaves with burn very quickly. Remove leaves to a paper towel and let drain as much as possible.
If desired, reserve a few leaves for garnish. Place the rest of the fried leaves in a small bowl or mortar and pestle and crush them.
Combine mayonnaise, sour cream, garlic powder, onion powder, salt, lemon juice and crushed curry leaves in a small bowl. Mix well to combine. Add in buttermilk to desired consistency.
Tastes great made fresh, or refrigerate overnight.
Notes
Deep fried fresh curry leaves will give you the best flavor, but if you can't get a hold of fresh leaves, you can substitute 2 teaspoons dried, crushed curry leaves.