Preheat your grill to medium-high heat for at least 15 minutes. Brush or spritz the avocado halves, onion and peppers with olive oil. Place everything on the grill – make sure the avocados, onion and limes cut-side down. Grill for 8 to 10 minutes, until grill marks appear. Be sure to continuously turn the jalapenos so the skin gets charred all over. Remove the veggies from the grill and let them cool.
Scoop out the avocado and chop it. Peel the jalapenos and remove the seeds, then dice it. Dice the onion – you might not use it all, it’s up to you. It’s easier to grill when kept in half though, so be sure to grill it all. You can add about 3 tablespoons of the diced onion to the guacamole and keep the rest for another dish or recipe.
Combine the avocado, diced onion and peppers, cilantro, juice of 2 limes, salt and pepper in a large bowl. Mash it with a fork until it reaches the desired consistency – chunky or smooth! Stir in the cotija cheese, leaving a bit for topping. Serve immediately!