get chicken breast and butterfly it, season with salt and pepper
sear using your method of choice (i barbecued it), until almost cooked through
transfer to whatever apparatus is suitable for your cooking environment, i used one of these bad boys;
but any oven-safe dish that can contain the chicken while keeping it all flat (so anything of that shape) is fine
pour on a good amount of tomato pasta sauce stuff, i used this;
generally u dont want to put so much pasta sauce in that it pools, just enough to cover like 75% of the breast same with the cheese
layer on mozzarella cheese (preferably buy a big ol clump of it and slice it up), generally enough cheese to cover 75% of each breast, more if ur a cheese fan (based). u can add other cheeses if u want just make sure they melt easy, otherwise the tradition is just mozz
return to heat source of your choosing and ensure it's closed (i just put the hood down on my barbecue and did it in there, burners on half heat)
monitor until cheese has melted. optionally u can wait until the cheese starts going a little golden on top, but if u plan on doing that i'd recommend taking the chicken off earlier than stated above as it might be overcooked by the time you get golden bubbly cheese
while i used my barbecue, pan-searing the chicken and then doing the cheese portion in the oven is certainly a good (if not better and more traditional) option
most important thing is to not overcook the chicken though no one likes dry chicken in their chicken parmy mate
oh and optionally garnish with freshly chopped parsley (death will come to you if you use anything other than freshly chopped)