Grind the dried shitake mushrooms in a blender, coffee mill, or spice mill. Do the same with the dried, chopped garlic. We like to grind our dried ingredients shortly before cooking to get the most flavor out of them. Combine the ground shitakes and garlic with the remaining rub ingredients. This yields about 1/3 cup of rub. You can keep any leftover rub in a small, air-tight container in the refrigerator for a couple of weeks.
Lightly coat the steaks with olive oil and coat generously with steak rub on all sides. Let rest for 1 hour at room temperature.
Prepare the grill for indirect grilling at 400° to 500°F with a hot searing zone. We recommend searing over an oak wood fire to achieve the best flavor for this recipe.
Sear the steaks on the hottest part of the grill. This can require as little time as 1 minute per side, or as much as 3 minutes per side, depending on your grill and your fire. Using a live oak fire on the K750 Hybrid Fire Grill, we seared the steaks for 1 minute per side.
While the steaks are searing, place the planks on the grill grate in the indirect zone to heat them up. After you have finished searing the steaks, flip the planks over and place one steak on each plank, keeping them in the indirect zone of the grill. Close the grill and roast for about 40 minutes total cooking time until you reach the desired doneness. For medium rare, remove the steaks from the grill when they read an internal temperature of 115 to 120°F. The temperature will continue to rise after they are off the grill.
During the roasting time, rotate the steaks as often as needed for even browning and cooking. Flip the steaks over on the planks half way through the roasting time. Keep the temperature below 500 degrees to reduce the chances of the plank catching fire. Use a spray bottle of water to douse any flames on the plank should this happen.
Remove from the grill, and place the plank on a heat-resistant trivet to serve. Caution, the plank will be hot. If you would like, you can transfer the steaks to a platter and remove the hot plank to a safe location. Carve the steaks to share after resting them for 5 minutes.