This quick protocol is the recipe for the best sandwiches I've ever made. You can be eating them within 15 minutes of your grill being hot, and they are superb. All ingredients available at your local supermarket.
Step 1: Ingredients
This is a four-ingredient sandwich: garlic naan bread, steak, cheese and baby spinach. The cheese can be whatever you like. The steak should be the best quality grilling steak you can bear to buy. You don't need much per sandwich.
Step 2: Steak
Get a decent steak - ribeye if you can afford it, sirloin if not. Cut off all of the external fat on the steak, but leave all internal fat. External fat drips and burns and smokes; internal fat melts and oozes into the meat making it delicious. Heavily salt both sides, rubbing the salt into the meat. I was recently introduced to Montreal steak spice, and I add that now along with the salt, but it's not necessary.
Get your grill started while you leave your prepared steaks to warm to room temperature. Once the grill (mine is a Weber Q, love it) is medium-hot (say 400°F), put your steaks on and close the lid. Turn after 4-5 minutes, then remove after another 4-5 minutes. If you have a reasonably thick steak it ought to be medium-rare (use a meat thermometer for added precision: you want the internal temperature to be 140°F). Don't overcook the steak - it will be dry and chewy instead of juicy and moist and delicious. Leave the steak on a clean cutting board to rest. Note that it continues to cook while you do this, so if you want medium-rare steaks, cooking them to rare is correct. If you pile them up, they will cook more.
Step 3: Naan
Grate your favorite cheese. I prefer blue cheese in this context, my family prefers Havarti (3rd photo here). Most of the photos show medium cheddar because the orange contrasts well for the photos and we had it in the fridge.
Throw a couple of garlic naan breads on the barbecue and grill for one minute covered, then flip. Sprinkle grated cheese on each bread and close the lid. Remove after a further minute, and plate.
Step 4: Assembly
Add thinly sliced steak to cheesy garlic naan, then liberally top with baby spinach. Serve. It's sensational. But don't take my word for it, make some yourself and impress your guests.