Rotate as needed until the skin is blistered and charred on all sides To char on a gas grill: Preheat the grill to high. When hot, add the chilies directly to the grates. Cook.
Place charred peppers in a bowl, then cover tightly with plastic wrap. Use a paper towel or kitchen towel to gently rub away the charred skin. Next, remove the stems and scrape out any seeds.
Place sour cream, loosely packed cilantro leaves, poblano peppers, chopped garlic, lime zest, lime juice, cumin, and a pinch of Kosher salt in the bowl of a blender. Process until very smooth, then taste and adjust seasoning. Refrigerate.