Cilantro Jalapeño Lime Mayo: Blend all the ingredients together until creamy and smooth. Pour into a container, cover and place it in the fridge until needed. During this time it will set up a bit more. 

Marinade: In a blender process all of the ingredients; except the oil, until smooth. Finally whisk the blended marinade with the oil until well combined. 

Chicken: Place the chicken inside a zip lock bag, pour in the marinade, close the bag, and move it around to ensure the chicken is fully coated. Or, coat in the marinade and keep in a glass/ceramic container and cover. Place in the fridge and allow it to marinade for about 6-8 hrs or overnight. 

Fire up the grill and set up a two zone grilling method. Half of the grill has charcoal (direct heat zone), and the other half doesn’t (indirect heat zone.) Run half of an onion across the grates to season and clean them. Lay the chicken directly over the direct heat zone to obtain grill marks and color. Then flip, and allow the other side to to the same. When you reach the desired color, transfer over to the indirect heat zone. Cover the grill and allow the chicken to fully cook (internal temperature of 165°F.) Then, lay the cheese over each thigh. Allow it to melt and remove from the heat. 

Buns: Spread both cut sides of the bun with mayo or softened butter. Toast over the grill. 

Avocado mash: Mash the avocados with the lime juice and salt until creamy but slightly chunky. 

Assemble: Spread the cilantro lime mayo over the bottom bun. Next, lettuce, tomatoes, and onion. Stack two pieces of the grilled chicken or you can do one. Spread some avocado mash on the cut side of the top bun and place on top the chicken. There you have it! A delicious Pollo Asado Sandwich. ENJOY!

Optional: Drizzle mustard and ketchup.