Combine cocoa, ground espresso and mushroom powder. Mix well.
Sear tenderloins on high heat for 1 minute per side. Allow to cool. Then evenly press the cocoa rub on all sides of fillet. Place tenderloins on medium- high grill for 5 minutes per side..
Remove from grill when internal temperature reaches 145°F (medium rare) or desired doneness. Allow to rest before serving.