Add the mayonnaise, sour cream, chopped dill, chopped chives, garlic powder, onion powder, MSG (if using), salt, black pepper, and ghost pepper chili powder to a medium bowl. Whisk well to combine.
Taste now to see if you think it needs more salt and pepper. I typically go heavy on the pepper. At this point it won't be quite as spicy as it will become after a few hours in the fridge. Double the ghost pepper chili powder if you want this to be Extra Spicy.
You can stop now (without the buttermilk) if you want more of a mayonnaise like consistency to spread on sandwiches.
Add buttermilk a little bit at a time and whisk until you reach the right consistency. I usually only need about 3 tablespoons to hit a thick dressing stage but if you're making this for salads, you might want to add more.
Store in a jar or container with a lid in the refrigerator for no more than 2 weeks.