To make these enchiladas, start by preparing the seasonings. Dice the onion and mash the garlic, setting them aside.
Next, heat a pan, on the stove, over medium-high heat and add in the oil.
Once the pan is hot, add in the onion and sauté it for 2-3 minutes.
Then, add in the mashed garlic and a pinch of sea salt and ground black pepper and cook it alongside the onion for another 3-4 minutes, or until it's nice and fragrant.
Use a fork to shred the cooked chicken breast. Add it to the pan with the onion and garlic and allow them to cook for another 3-4 minutes before removing it from the heat.
Next, preheat your oven for 350 F.
Assemble the enchiladas by laying the out tortillas on a countertop and spray both sides of them with oil.
Grab an 8x8 baking dish and pour 1/4 jar of the salsa into the bottom of the dish.
Next, fill each tortilla with some chicken mixture and roll them up tightly.
Then, place the enchiladas, folds-side-down into the baking dish. Repeat until all of the enchiladas have been assembled and the tray is filled.
Pour the remaining salsa on top of the rolled enchiladas, and sprinkle the shredded Mexican cheese on top, if using.
Finally, transfer the baking dish to the oven for 20 minutes. If you want, you can turn on the broiler for 2 minutes at the end, so that the cheese gets browned.
Once it's done, remove it from the oven. Add any garnishes on top that you desire, then serve and enjoy!