By hand method: Finely mince the cilantro. Mix it together with the remaining ingredients.
Food processor method: Place all ingredients in a food processor and whiz for a few seconds until combined.
Blender method: In a regular blender or using an immersion blender, blend all ingredients starting with 3/4 of the sour cream until combined. Stir in the remaining 1/2 cup sour cream (this prevents it from becoming too runny).