Mince garlic and fresh rosemary. Coat steaks in a thin coat of olive oil. Season with salt and pepper to taste. Spread some of the minced garlic and rosemary on both sides. Place mushrooms on foil, coat in olive oil, salt, pepper and garlic and rosemary. Wash Shishitos and coat in olive oil and garlic.
Light charcoal with a chimney starter *DO NOT USE LIGHTER FLUID!* just a suggestion, but not really. let steaks come to room temp while fire goes. Dump coals when white hot and cover grill, allowing grates to heat.
Throw on the wrapped package of mushrooms. Drop steaks on the screaming hot grill (550 degrees f +) For 1.5 inch steaks cook 2.5 minutes then quickly give them a quarter turn. Flip, repeat, remove. Finally, using tongs, put shishitos on the grates, cook, flipping every 30 seconds until soft and blistered.
Let the steaks rest, covered for 5 minutes. Slice against the grain, plate and enjoy!