Step 1 - For the green sauce: In a bowl place the onions, garlic, cilantro, parsley, oil, vinegar or lime juice, salt and pepper. Stir to mix well and let stand for 20 to 30 minutes.
Step 2 - Serve the locos on a platter or plate, on lettuce leaves with a little mayonnaise on top of the locos. Serve the salsa verde on the side to accompany.