Prepare your charcoal grill for a high heat direct cook. Remember that the vegetables need some charring, and won’t be on the grill for too long.
Place unpeeled garlic cloves onto an 8” x 8” piece of foil. Top with a small amount of oil. Gather opposing sides and ends and seal packet. Make sure there is a little room for steam to build.
Wash tomatoes, jalapenos, and pasilla pepper. Blot dry with paper towels. Brush with olive oil.
Peel the onion and cut in half. Brush with olive oil on all exposed parts.
Place vegetables and garlic packet onto the grill and cook until skins take on a brown appearance and skin begins to pull away from the tomatoes. You will have to stagger the cooking times on each item as some things cook faster than others. Remember to rotate the vegetables to get an even browning on each side.
Remove vegetables and garlic from the grill and place them onto a clean plate. Let them rest for 10 minutes or until cool enough to handle.
Remove the skins and seeds from peppers and tomatoes and place them into a food processor along with the cooked and peeled garlic. Roughly chop the onion and add to the rest of the vegetables. Add lime juice and a few pinches of salt and pulse 8 (or more, depending on preferred consistency).
Taste for flavor and adjust accordingly. Transfer salsa to an air tight container and store in the refrigerator for 4-24 hours. I recommend making this this salsa the day before you're planning to serve it.
Right before serving, chop half of the cilantro and stir into the salsa. Add the remaining whole leaves on top as garnish.