Heat up a cast iron skillet over medium heat. Lightly oil the pan and add one mushroom to the pan and get it used to the heat. Lightly salt the mushroom.
Using a heavy dish or another skillet, begin pushing down on the mushroom and gradually increasing the pressure until it resembles a steak. You will want to push pretty hard to compact it down to a meat-like thickness. Sear the mushroom on both sides and remove it from heat. Repeat with the other mushroom.
In a small bowl or tupperware, add the marinade ingredients and set your seared mushrooms in it. Cover and let sit for 10-20 minutes.
While they are marinating, heat a grill to medium-high heat.
Remove the mushrooms from the marinade and sear them on the grill over medium-high heat for a couple of minutes on each side until charred. Alternatively, you can return them back to a hot skillet and sear them that way. Add the mushrooms back to a hot pan and sear for a couple of minutes on each side until slightly charred.
Baste with the BBQ sauce on each side and serve warm. Leftovers keep in the fridge for a day or two.
