Add mayonnaise, buttermilk, and sour cream to a medium bowl
Whisk until completely smooth with no lumps
Add parsley, dill, garlic powder, onion powder, salt, and black pepper
Whisk gently until evenly combined
Taste and add a pinch of sugar if desired
Leave as-is for dip consistency or add milk 1 teaspoon at a time for dressing
Cover the bowl and refrigerate for at least 30 minutes
Stir once before serving
Notes
Resting time is essential for smooth, mellow flavorUse dried herbs only for authentic Dairy Queen tasteAvoid vinegar, lemon juice, or fresh garlicFull-fat ingredients give the closest restaurant-style textureFlavor improves after several hours or overnight