Heat the grill to medium-high heat. Drizzle tomatillos, onion, garlic, and poblano pepper with olive oil and a few pinches of sea salt. Wrap the garlic cloves in foil with a bit of oil. Place all the vegetables directly on the grill. Grill until they are soft and slightly charred. Remove veggies from the grill and unwrap the garlic. Allow to cool for an hour.
Put all the ingredients in a blender and blend until smooth. Taste and season as necessary. Refrigerate for up to four days.
Serve as is or with whatever garnishes you like. Select garnishes, like those suggested, which will add flavor and crunch.