In a large bowl, add the butterflied chicken breast, canola oil, and all of the blackening spice. Using tongs, turn the chicken breasts over a few times to fully coat them in the spice & oil. Cover the bowl and refrigerate for 20 minutes to marinate.
After the chicken breasts have marinated, in a large deep skillet, pour the chicken breasts and all of the spice/oil mixture into the pan.
Over medium heat, cook the chicken breast until well done, flipping regularly, about 15-20 minutes.
(Optional) Turn the heat to low and add the cheese onto the chicken breasts. Cover the pan with a lid and let the cheese melt for 1-2 minutes.
Remove chicken breasts from the pan and transfer them to a plate lined with paper towel to remove excess oil. Set aside until you are ready to assemble the sandwich.