If making in a blender, place sour cream, loosely packed cilantro leaves, garlic clove, lime zest and juice, and a pinch of Kosher salt in the bowl of a blender, then process until very smooth.
Whisk together all ingredients until smooth. Cover and refrigerate until needed.
Store leftovers in an airtight container in a refrigerator. We like to keep crema in a little squeeze bottle for easy serving!