Butterfly cut two chicken breasts, so you have four thin chicken breasts.
Season with onion salt and pepper on both sides
Heat 2 tbsp. olive oil on medium heat. Add the chicken breasts. Cook for 3-4 minutes on each side. Remove the breasts from the skillet and set aside on a plate.
In the same pan, add the butter. Let it melt a bit and then add the garlic and parsley. Stir it all together for about a minute on low heat.
Add the chicken back to the pan and using a silicone spatula, pour the garlic/parsley butter sauce over your chicken as best as you can. Cook for another minute or two then remove the skillet from the heat.