Position your oven rack to about 6 inches away from your broiler.
Preheat the broiler. While it preheats, cover a baking sheet with tin foil.
Spread the chiles out over the baking sheet and hit them with a drizzle of olive oil; toss to coat them evenly.
Pop the baking sheet into the oven and broil the chiles for 5-7 minutes—or until the skin is starting to char and bubble. Then, carefully with tongs, flip them over and broil for another 5-7 minutes. When both sides of the chiles are charred, take them out of the oven. Set them aside and let them cool before handling.
Once the chiles have cooled down, peel them and slice them open; discard the seeds. Roughly chop the chiles and store them in the fridge within two hours.