Promptly add the green onion and parsley. Add the garlic, and stir to combine. Then stir in the sour cream, all of the butter, and the salt. Season to taste with additional salt (I usually add another ¼ to ½ teaspoon) and freshly ground black pepper.
2 tsp salt, ⅓ cup chopped fresh parsley, ⅓ cup finely sliced green onion, mostly green parts, 1 garlic clove, ¼ cup sour cream, 3 tbsp butter, black pepper