1. Toast pumpkin seeds in a dry heavy skillet over low heat. Stir frequently with a heat-proof spatula, until seeds puff (but NOT brown), about five to seven minutes. Let cool.
2. In a food processor, puree toasted pepitas, garlic, parsley, scallions, oil, water, lime juice, cumin, salt and pepper flakes (if using), until smooth. Thin with a bit more water if desired. Taste for seasoning and adjust if needed.